The Pamphlet Collection of Sir Robert Stout: Volume 33
Although I have much pleasure in addressing you on a favourite subject, I yet feel some little embarrassment, for I may mention, in the first place, that the subject is not of my selection. I should have preferred one admitting of experimental illustration, as I am in the habit, in the course of my practice as a teacher, of operating while I talk, and, therefore, even from force of habit, like to have something to do with my hands. Again, it is obviously impossible for me to pretend to show to all of you the objects themselves; still, although a friend of mine told me in this room that the lecture would be of no use without such demonstration, I will try with the instruments I have before me, and the drawings you see on the walls, to elucidate the subject. Another point that occurs to me is, that while in class lectures I am in the habit of at once plunging into the subject, giving out the heads, and then working them out step by step, the microscope is too discursive a subject to admit of that treatment, but requires much introduction; for, even in the first place, to explain its construction and operation we have to call in aid the two special sciences—optics and mechanics, to be followed by chemistry; and page 190 when by these means we have our instrument completed and in working order, our sphere of action is then the domain of entire nature, diving into the earth to examine minerals, dissect fossils, then tracing vegetable growth, and so upwards till we come to the highest classes of animal structure, all distinct sciences within themselves, and not easy to link into a regular chain. We will, however, make some attempt towards it.
Note.—This is a very much abridged report, in fact, a mere outline of the lecture, and several topics are altogether omitted. But it must be conceded that it was a difficult lecture to report, as much front the manner of delivery as from the number of technical terms and names which could not ha excluded. Had I changed places with the reporter, I doubt if I could have done better for him. I hare sketched in a few blanks, but memory is the only record I have of what was actually said.—S. G.
A public audience expects to be interested as well as instructed, and looks for something in the way of exordium. Now, I have not yet decided what kind of exordium I shall offer you, but may take a hint from Virgil, who, in dealing with a not very remote subject, expresses himself in terms which I may thus paraphrase, viz., that, "it being a minute one, some may consider it trifling, but the importance is not commensurate with the minuteness, nor is the honour and glory of dealing with it as small as the objects themselves;"* that is, he quaintly adds, "if the fates only let one alone, and Apollo hears when invoked." In another similar place† he promises not to detain his readers "with a made-up story, or by meandering or a long exordium." I would wish to follow his example.
Let us take the first object to hand (as I now do from the table before me) as a starting point. We look at it, feel it, and so acquire a certain knowledge of its more obvious properties, but say that for our purpose that does not suffice; we require to know more than our unaided senses can tell us—to enlarge the minute—to examine by increased light, transmitted from below or reflected from above—to obtain the relief of light and shade; in a word, we need the help of the compound microscope, of which by means of the model before me I will endeavour to show you the arrangement, and the passage of the rays through this combination of lenses producing the image required.
From every object perceived by us rays of light radiate in all directions, as instanced in the diagram before us of a lighted candle. Now the greater the distance we are from the candle the fewer of these rays enter our eye, for, suppose this foot-rule to be the diameter of the pupil, if I place it at a certain distance from the candle it receives four of the rays depicted; further off, two; nearer, six and more, and so on.
* Georgic iv. 6.
† Georgic ii. 46.
Now the apparent size of an object depends on its distance, and bearing this in mind, it follows that the farther off an object is from us the smaller is the angle it subtends at the eye. Instinctively, if we want to examine an object more minutely or with increase of light, we bring it nearer the eye, and when we can get some instrument to do that for us we have achieved much. Now, it is the lens that accomplishes this, the rays of light being bent and undergoing what is termed refraction in passing through it to form the image on the other side; and it is an important point to remember that the eye sees the object in the direction of the rays which enter the eye without reference to that of the rays outside the lens, the refraction being the greater according to the convexity of the lens; so that, as in the model diagram before us, the object presents itself to our eye, not in its real position and dimensions, but nearer and enlarged, because viewed under a higher angle.
The rays, having passed through the lens termed the objective, have to pass through a second and upper lens (the eye-piece) to reach the eye; and here let mo mention that, although I have commenced by explaining the compound microscope, I might have introduced it to you in the first instance in its simplest form, viz., the ordinary pocket lens, familiar, I presume, to most of us, and with which a great deal of work may be done. Mount it on a pillar, and you transform it into one capable of adjustment; you may make one lens of the group an illuminator to another. If a higher power is required you have recourse to a Coddington, an excellent instrument, and far superior to the popular Stanhopes sometimes sold for it. Then there are the Wollastons, with one, two, or three lenses acting together, and magnifying the object itself directly, and not the image.
[The lecturer here went into some practical and technical illustrations of the construction and manipulation of the instruments before him, which cannot well be followed on paper, remarking that to such a delicate pitch had instruments been carried, that powers up to 1/50 th had been made, but that they were very difficult to use, and limited in their application; also as to various contrivances employed when an object that has been mounted before is again required for view, it becoming then sometimes a matter of importance and difficulty to find it, such as Maltwood's finder, a plate of glass on which a square inch is marked, divided into 100 each way, every square having two numbers, one for latitude, page 192 one for longitude; and which, by putting in the place of the object and duly marking, furnishes at any future time a certain indication to find the object; also the admirable contrivance of Powell and Leland, in which every stage movement is graduated, so that the position of the stage and of the object on it during any given observation can be registered. He then went on to say:—]
Let us now say something about the objects themselves, as illustrated on a magnified scale in the various drawings covering the wall before you, and which I may parenthetically observe are all supposed to be lighted from one point, and calculated to be best seen at a distance of about twenty feet.
I shall not trouble you with any remarks as to the mounting of objects for microscopic observations, but proceed at once to state that the first object that we have for consideration in dealing with organic matter is the cell, the primary form of which is that of a simple closed bag with contents, the form varying very much indeed, but the typical form being round; and the contents varying also greatly in both animal and vegetable products, but yet so closely allied in lower grades as to render it difficult to distinguish between them. A notion has sometimes been advanced that there is a gradual elevation of structure from the vegetable to the animal kingdom, and popular writers often mislead their readers by describing as "links" objects that appear to partake of the character of both. There is no such progression. The two kingdoms diverge from a common boundary, and that is the lowest type of each—viz., the simple cell, which it is often difficult to refer to its right place. Many mistakes have been made in this matter, and a large portion of the microscopic work being done now is the distinguishing between plants and animals, and referring back to the vegetable kingdom many objects formerly classed as animal, particularly by the celebrated German Ehrenberg, who, while it must be confessed that he has done enormous work, must also be charged with giving the microscopists of the present day a very large amount of work in undoing his classification, arbitrarily founded on hasty conclusions as to the existence of prehensile and digestive organs in what are now proved to be vegetable organisms destitute of both.
A simple vegetable cell consists of an outer coating called cellulose, nearly akin to the substance we know as wood; and inside that a thin lining, known as the primordial page 193 utricle, containing nitrogen, and it was this nitrogen that was for a long time one of the principal difficulties in the way of classifying the low forms of vegetable and animal life. Starch was considered at one time the distinguishing characteristic of vegetable, nitrogen of animal life; but now we find that substances very akin to starch exist in animal bodies, as in the base of the brain in man, so closely akin, indeed, that at present we do not know how to distinguish them from it;* while, as I have just mentioned, nitrogen is to be found in the inner lining of vegetable cells.
Inside this cell is the protoplasm, a viscid substance which is, in fact, the growing material, such being the signification of the term, and with it is generally to be found some colouring matter, as chlorophyle.
The figure I now draw your attention to illustrates the growth of the cell, which multiplies by simple division, a proceeding a little at variance with the ordinary course of arithmetic. First of all we see the protoplasm divide itself in the original bag, gathering itself into two bodies, and then the outer coating becoming constricted, these bodies are severed, and the development has taken place. Now let me draw your attention to this illustration of the plant palmella cruenta, or blood-rain. We hear sometimes of frogs in stones, of which there are no authenticated cases to bear proof, but there are other things nearly as wonderful, and one of them is the amazingly rapid growth of this plant; the blood-rain does not appear as a liquid, and no one sees it coming down, but it shows almost suddenly as clots of blood coagulated on the ground.
* Lerp-Amylum, a constituent of the insect secretion on a variety of Eucalyptus (dumosa), is another example.
Now, proceeding a little higher in the vegetable scale, we come to a very curious object known as the volvox globator, which, by the way, was one of those described by Ehrenberg as an animal, but which may be simply described as consisting of a number of small vegetables enclosed in a common envelope, as here depicted. These plants are all aquatic, and have a remarkable power of movement, sometimes spinning along with great rapidity, at others remaining in one place but revolving with as great rapidity. It is a globe containing, or rather consisting of, a number of smaller ones, each of which is an individual, and is in due time discharged from the family group to enter upon its independent existence. Another illustration of this family before us is the gonium pectorale—so named from a fancied resemblance to the Jewish high priest's breast-plate—a group of sixteen cells spinning along on edge, and as the time arrives for each little plant to be sent into the world, it is simply cast off, and the remainder of the group goes spinning along without it. In course of time the one left opens into four, these each into four more, and so the original number of sixteen is arrived at.
Here again is the picture of the plant Zygnema, with several others akin to it, and known as confervœ, and which you will find in all the fountain basins in the Fitzroy Gardens, in the shape of a green, fibrous-looking fringe overhanging them. You remember the old fountain in Collins-street at the time when attempts were made to get up a panic about the Yan Yean water, and that when this green growth made its appearance on it, an outcry was raised that all that horrid green stuff was in the Yan Yean water, such simply not being the fact at all; the plant was local, and its growth was favoured by the constant moisture. It presents the curious phenomenon of conjugation, the adjacent cells on different plants uniting, and their contents blending, to form a sporangium, which ultimately gives rise to a new growth.
We now come to another class of objects which were page 195 regarded as animals by Ehrenberg, who appeared to have considered everything small and moving as an animal; but that test has been long since given up, for many plants are much more active than animals, moving with a rapidity indeed that would be incredible in an animal, while you cannot find a vegetable much quieter than the oyster, or, better still, the sponge.
We now come to the Diatomaceæ, of which each individual is complete in itself, but not having a skin or woody shell, but one of glass or silica. These shells are extremely beautiful and of endless variety of form, forming constant objects of interest to the microscopist. Amongst those here depicted I may briefly enumerate (pointing to each) the actinocyclus, a circle with rays; the coscinodiscus, the eupodiscus, the triceratium, the Biddulphia, the Arachnoidiscus, from its similitude to a spider's web. Of a slightly different class are the Pleurosigma, the surirella, the gom-phonema, the melosira, the navicula, &c.
All these consist of two of the shells I have spoken of with a little organic matter inside; and in addition to these discs or other forms here depicted, of which there are two in each plant, there is also a little hoop of glass or silica connecting them. This hoop is elongated, the valves being pushed out, and a new pair of plates formed between the others, and then the two uniform bodies separate. Some of these forms adhere together, attached to a stalk, and this variation forms one means of classifying them; here is another kind, presenting the appearance of a row of little rods slightly adherent, but which keep on sliding nearly apart and then back again with great regularity.
Richmond, Virginia, U.S., may be said to be built on these objects, for the soil there contains them in abundance for miles; or, to come nearer home, here is a bottle of white powder representing a portion of the railway embankment at South Yarra, just by the tannery, familiar, probably, to most of you, and which has proved very rich indeed in these objects. Before the work was constructed there was a swamp there, and the earth was dug out from the sides and thrown up to form the embankment, but the ground being swampy the work sank down and the mud underneath oozed out, rich in the most beautiful forms, some forty different species being found in it.*
* By Messrs. Ralph and Coates, who were before me in that field.
This subject of the South Yarra embankment suggests the remark that the nomenclature of these objects is somewhat confusing, and people at a distance from each other, finding some object new to them, often consider it new to all. There was one of the shells I have been referring to which was exhibited here as a total novelty, but within a week of its exhibition I received a letter from England asking me to send the writer some of "'that' Stauroneis Fulmen, from South Yarra," so that after all it proved to be known and named in Europe before it was recognised here.
But the feature which, more than the beauty of the forms, has endeared the Diatomaceœ to the microscopist, is the possession of delicate markings, varying in the different kinds, but tolerably constant in each. These markings, which usually consist of a groundwork of very fine lines, are, and long have been, used to test and compare some of the power's of microscopes. Not content with making out these lines—many thousand of which go to the inch—microscopists are ever striving to get beyond that feat, and to define what the lines are made of—whether mere dots, areolations, elevations, depressions, Some of the earlier photographs showed these as hexagonal areolations, but more recent observation supports the view that the lines are rows of hemispherical elevations. For many years I have been satisfied that the lines in the Pleurosigma formosum, which I have most closely examined, are so formed; but when I made the observations, the microscopic world was satisfied with the views which are now going out.
We now come to speak of the spore which is formed by the union of a pair of cells, and which eventually becomes developed into a new plant. Several varieties appear in the drawings before us. We must not omit to notice here a very remarkable order of plants, viz., the Desmideœ, which nearly resembles the Diatoms in habit and mode of propagation. There is, however, this essential difference, that while the latter are silicious, the Desmids are wholly composed of vegetable matter, chiefly bright green colouring. They are found in sweet, pure waters, and in no others do they thrive. In this group—which represents the varieties that I have found in the Yan Yean—is seen a great variety of elegant forms, while in the adjacent drawings, representing the same water after contamination, as found in the gutters, but few are to be seen.
Ascending upwards in the scale we have to note the fungi, page 197 containing more nitrogen than some of the other plants, growing with great rapidity, and more or less characteristic of putrefaction, preferring decaying matter, chiefly animal. There are, in fact, some of the fungi which blow-flies mistake for meat.
These plants do not possess so much interest for us as those whose beautiful forms and curious habits have already occupied our attention; they are nevertheless of more real importance, since from their ranks we derive, on the one hand, esteemed delicacies, and, on the other, poison and the associates of disease. The scientific distance between the truffle of our paté de foie gras, the deadly amanita, and the oïdium of the fatal diphtheria, is hardly greater than between the rose, apple, and peach, which are all of the same natural order, rosacea;. But I may mention two or three varieties. Apart from the mushroom and the truffle, there are several poisonous kinds; and others, again, which, although suspected, are still alleged by some to be very good and wholesome. Then we have the common mould, that beautiful little plant, of which cheese-fanciers are so fond. Viewed with a reflected light from one side, and with a binocular arrangement, it is a magnificent object for inspection, showing as a forest of little trees, each tufted with a crown of bright globules, and all the other moulds are more or less of the same kind. There is yeast, called by the Germans ober and unter-hefel; the ober, which is the aerial fructification, being diffused in the air as dust, the unter settling to the bottom. There is the oïdium attacking the grape, and that affecting the human throat in the case of diphtheria.
A remarkable fungus, which has given rise to the mistake formerly noted, is the Sphæria, found, among other places, in Tasmania; it has also been seen in the vicinity of Melbourne. I have seen in print vague accounts of the remarkable link between the animal and vegetable existing in a body, which was plant at one end and caterpillar at the other. It was this object, of which several are on the table, viz., the Sphœria, growing, as is its wont, out of the head of a caterpillar, which its germination as a parasite had killed.
Still ascending in the scale we come to ferns, and the peculiarity to notice here is the fructification, which consists of a large number of little capsules, or hollow cases, called sporangia, generated on the surface of the under side of the page 198 leaves, and shown in the diagram before us in the markings extending along the margin of the frond.
Each sporangium contains a number of granular particles, or spores, a something partaking of the nature of a seed, but still not a seed, but something from which the growth springs. This spore expands under the influence of heat and moisture, and develops into what is very much like a little leaf, and is called thallus, and from certain organs in that thallus a new plant is produced, distinct altogether from the spore.
We now come to plants of a more complex texture, where there is differentiation of organs, where one cell may go to form bark, one to form wood, another to the reproduction of species, &c.; but we have still cellular tissue, and organs formed from it, as, for instance, the strawberry, a fruit of very loose texture, with large cells preserving their rounded form. But when cells are compressed we get an hexagonal structure, network-like. And in this question of pressure we have to consider not merely the pressure itself, but its direction; thus, when the longitudinal increase is greater than that of breadth, or thickness, the cells are elongated while they are laterally compressed, and we have the fibres of wood; flax, which consists of such elongated cells joined end to end, may be quoted as a good example of woody fibre. In cases of very loose structures, where the growth of the plant is rapid, this internal pithy tissue is frequently torn away in the middle, and the pith is sometimes broken up into discs, or spirals. We get in some woody tissues markings of a peculiar character, sometimes spiral, sometimes disc-shaped, as instanced in this section of fern, showing ducts, or long hollow bodies, with traces of spirals. The seed of the common cress, when moistened, appears to exude a jelly; this consists of spiral fibres, forming originally the outer part of the shell of the seed, which the water releases from their confinement.
Another vicissitude occurs with regard to the process of filling up; in secondary deposit forms there is a continual deposition of matter taken as nutriment in the interior of the cell, sometimes soft, sometimes hard. In the core of the pear, for instance, there is, as you know, a gritty portion, that gritty portion consisting of a number of these cells flattened. In some rushes the cell is altered from its round form into a star, the rays of which spread out to reach their neighbours. A denser variety, in which the page 199 cells are nearly filled with the hard deposit, constitutes nut shell.
The diagrams now before us show the arrangement of the stomata or breathing pores existing in great numbers, chiefly on the under sides of the leaves of plants, by which the air and moisture are taken up and passed into the cavities inside, as instanced here in the oleander, where a cavity is protected by a number of hairs furnished with a multitude of pores; or again in the balsam. These views of the cuticle of the lily and aloe show the peculiar arrangement of the cells by which those immediately surrounding the opening form lips which almost seem to serve as valves.
Another feature worth notice is that of the crystals existing in many plants, found to be principally composed of oxalate and phosphate of lime and other similar earthy salts.
Among the most important of the vegetable matters of which the microscope takes cognisance, and one in which its usefulness is remarkably shown, is starch. Although all starch is starch in a chemical sense, there being no difference of composition between the expensive arrowroot of Bermuda and the similar product of the humble potato, still the difference of form is very great, and by the aid of the microscope the starches of known plants can be distinguished with unerring exactness; not merely for the detection of adulteration or substitution, but as data useful to the juridical expert, who utilises items of information in which others would not perceive any pertinence.
The use, too, of polarised light, which marks each individual particle with a black cross, is in such observations of singular value, as from mixed fields it instantly weeds out all the starch, leaving us the residual matters to deal with.
We now come to animal life, the simplest form being indistinguishable from the simple vegetable cell, a rounded hollow bag with something in it, and very often little cilia or filaments attached to it by which it swims about.
Starch and nitrogen, although useful aids, are not then sufficient in themselves to distinguish between animal and vegetable, and we have already seen that motion, power of selection, and apparent volition are highly deceptive. Fortunately, with the discovery of the fallacies attending the old tests, new and more satisfactory ones have been acquired. Plants assimilate simple substances from the inorganic kingdom, and build them up into complex forms. Animals page 200 require for their food these complex bodies, which by decomposition they ultimately simplify.
The Proteus, so called from the multitude of forms it can adopt, is merely a little dot of jelly containing a few bubbles, lazily rolling itself along in the water without limbs or organisation. But it makes what limbs it wants when it wants them. You may see it pushing forth something like a leg, and then another, sometimes apparently for diversion, but at other times for locomotion or food. When it swims or rolls up against anything good for food, it simply surrounds its dinner, forming its whole body into an extemporaneous stomach.
Closely akin to this, in fact belonging almost to the same class, are some beautiful objects, which for a long time were placed higher up in the scale, the Foraminifera.
They have extremely beautiful shells, of most elegant forms, all very minute, but still varying much in size, although the largest does not exceed the size of a very small pin's head. They are very widely diffused, so much so, that by a figure of speech the pyramids may be said to be built of them, as they are built of stone, which consists in greater part of these fossil shells; and to refer to a more familiar subject, you find them plentifully in new sponges.
Then come the Polycystina, very beautiful shells, varying much in form, and composed of silica.
[The lecturer said that he had refrained from encumbering the minds of his hearers with any more technical nomenclature than was necessary. To show that such as he omitted would profit them but little, he recited the names of a dozen of each of the last two genera which formed the illustrations.]
And now having worked up to animals, I think I may introduce you to the waters, in which, as was the case with plants, we find the simpler forms. Here is a group showing the natural history of the Yan Yean in 1859, all animal and vegetable forms, but yet consistent with perfect sweetness and wholesomeness of the water, for this very good reason, that the majority of them would not live in anything else. Several of these animals are furnished with cilia round the mouth in continual motion, producing the appearance of a wheel going round, or like that peculiar appearance you may have observed in a field of corn when moved by the wind, and appearing to progress, but not doing so in reality. Hence these animals are called Rotifera, the object of the motion appealing to be the attracting, as with page 201 a whirlpool, smaller animals into the vortex of the mouth. This drawing represents a comparatively large animal of this species with two wheels, and a very pretty experiment may be made with some dry particles of carmine or indigo thrown into water with these animals, when the floating particles indicate the direction of the current.
A word or two now about parasites, and to which I ask your particular attention. They are very ugly and very injurious, and they are external and internal.
There are external ones, such as the flea and bug, microscopically beautiful, and some very remarkable ones of the family of the Ixodes. If you kill an opossum you are certain to find in one, if not in each ear, one individual of this family, with a curious kind of mouth opening outwards with a kind of claw similar to a "lewis," a tool used by masons for raising stones, and which proboscis the animal will suffer to be torn off before it gives way. There is the Demodex, living in or near the skin of animals, and not migratory; as, to take a familiar instance, in the region of the face, chiefly in the neighbourhood of the nose, are specks, which, on being squeezed out and examined, are found to contain minute animals, something like maggots; unlike other parasites, this kind bears no relation to either disease or dirt. Here is a magnified photograph of the sheep scab, Sarcoptes ovis, from this original specimen, and here is an enlarged drawing of the animal. But the class of parasites I wish more particularly to speak about is that of Entozoa, an internal one, living within us; not a very pleasant subject, but a most important one.
The trichina spiralis is ordinarily known as indicative of measly pork, although the name measly is rather a misnomer. Here is a view of muscle containing an oval-shaped bag termed cyst, in which is coiled up the parasite. This is found very generally in pork; it is scarcely possible for any but dairy-bred and dairy-fed pigs to be without it; in fact, I very much question whether any pig exists that is free from it. It is commonly said that pork ought to be well done, but I assure you these things take a good deal of doing, for in some stages of existence there are both animals and plants that survive an enormous amount of ill-treatment; and it is a question among naturalists of the present day whether boiling is sufficient ill-treatment. Many germs are known to survive a temperature of 300° Fahr., hence the mistakes of those who entertain the idea of spontaneous genera- page 202 tion, and who fancied that because they boiled their preparations all germs had been excluded. So far from this being the case, recent rigorous experiments have shown that some of the germs, both animal and vegetable, the destruction of which is most desired, will endure remarkable vicissitudes of temperature, and even resist many reagents. These (trichinæ) are particularly long-suffering creatures. Many people are in the habit of eating pork slightly done; in Germany, for example, it is often merely smoked, with but little more cooking; and in that case the trichina simply becomes an inhabitant of human muscle, increasing and multiplying very rapidly. That such is the fact is exemplified by this portion of human muscle, taken in Melbourne, and which has multitudes in it. I do not suppose that Moses knew anything about the trichinæ, but the disease they cause may then have been known; and the prohibition of pork in a hot climate is undoubtedly a wise thing. The two drawings to which I now direct your attention show the figures under different conditions of a variety of the tape-worm, sometimes growing to the length of 30 or 40 feet. This kind normally inhabits dogs; and there is every reason to believe that the presence of them in human beings is often due to carelessness in allowing children to play with dogs, and the latter to lick their faces. I have here some ugly things for which I am indebted to our health officer, Mr. Girdlestone. They were taken from a pork kidney, and belong, we believe, to a kind called strongylus. But at present the kinds best known are extremely large, and whether these are young ones or a variety is not yet determined, but probably soon will be; for while the kidney was under examination, a cat stole a portion of it, and from a plump, fine animal it fell away, and is now decidedly out of condition. It will soon be sacrificed in the cause of science; so that the fate of that marauding cat may point a moral, and its tail adorn—a museum.page break
Mason, Firth, and M'cutcheon, General Printers, Flinders Lane West, Melbourne.