Description of Figure 2.

Fig. 2. Section of anterior portion of lower jaw of fœtal calf, Bos taurus, taken in an antero-posterior or sagittal direction; showing the enamel organs of two teeth, one larger and the other smaller, in situ. The section has passed through the lateral portion of each tooth; and as the incisors in this species have their crowns laterally expanded, whilst their fangs are compressed from side to side, the central stem of the dentinal pulp is not seen in this section, and the enamel organ passes entirely round its lateral expansion. The dentinal pulp itself is not represented in either of the two teeth; two contour-lines, bounding the apical half of the space which it occupied in the larger of the two teeth, show the extent to which the deposition of enamel and dentine severally had proceeded upon it. In the smaller of the two teeth the deposition of enamel has not commenced, and the enamel organ has as yet suffered no diminution of its "spongy," or "gelatinous," or "stellate "tissue. This drawing being semi-diagrammatic, segments only of the histological elements making up the epithelium of the gum, the epidermis of the lip, the tooth-sac, and the enamel organs, have been given; the contour-lines prolonged in each case from the external boundaries of these segments, appearing to indicate sufficiently the relations held in nature by the several structures.

a.	Anterior surface of lip.
b.	Epidermis of lip.
c.	Epithelium of gum.
d.	Tooth-sac, which at this stage in the development of the tooth, and before it receives any support from the bony structures in the jaw, is clearly marked off by layers of condensed cellular tissue from the strata of cutis vera, which are interposed between it and the external epidermis. The loose spongy central portions of the tooth-sac bear some resemblance, when viewed with the unassisted eye, to the similarly placed stellate element of the enamel organ; they differ from it, however, by page 2 being vascular, and even highly vascular; whilst they differ from the cutis vera, not merely by their greater looseness of texture and their greater vascularity, but also, as seen in the figure, by the absence of glands, of hair-bulbs, and of muscular tissue.
e.	Enamel organ. From the point to which the line e is drawn, downwards, the enamel organ of the larger tooth is seen to possess all the three structures; viz., the inner epithelium, the stellate or spongy tissue, and the outer epithelium, which the enamel organ of the smaller tooth (h1) still possesses. Above the point to which the line e is drawn, the stellate tissue has disappeared, and the two layers of the enamel organ's epithelium have come into apposition. Thus the epithelial cells of the inner layer, which produce the enamel prisms, or "fibres," come into closer relation with the bloodvessels of the tooth-capsule, whence alone, in the absence of vessels in the enamel organ, they can provide themselves with the requisite mineral matter.
f.	Space in the larger tooth occupied by the laterally projecting portion of the spoon-shaped dentinal pulp.
f1.	Corresponding space in the smaller tooth: in neither tooth did the central stem of dentine come into view in this section.
g1.	Contour-line indicating the extent to which the deposition of enamel has proceeded in the larger tooth. This line corresponds to the similarly lettered granular deposit in fig. 1. Internally to this line, a second line is seen describing a similar contour, but reaching considerably further down. It indicates the extent to which the cap of dentine reaches downwards upon the exterior of the pulp; this extent being considerably greater (as is seen also in fig. 1) than that attained to by the deposit of enamel at this period of development.
h and h1	Line of junction, in the larger and smaller tooth respectively, of the stellate tissue of the enamel organ to its inner layer of epithelium. In both enamel organs the outer layer of epithelium is drawn as more nearly columnar than it is in nature.