1436 HUMAN ANATOMY. 



the ultimate fibrillae terminate in minute bead-like endings that lie free between the 

 epithelial cells, either near the free surface or at a deeper level. 



The nerves- distributed to the taste-buds — the intrabidbar fibres — enter at the 

 basal pole. Usually numbering from two to five for each bud, on gaining the 

 interior of the latter they undergo rapid division and become numerous. A majority 



of the resulting fibrillae ascend in tortuous windings 

 Fig. 1 197. ^^ towards the apex of the bud in the vicinity of which 



some end, while others recurve and end at lower levels. 

 The fibrillae terminate in free, usually minute knob-like 

 endings, that lie between and often in close contact with 

 the supporting and gustatory cells. It is probable that 

 in no instance do the nerve-fibrillae actually unite with 

 the gustatory cells, the relation being one of apposition 

 and not of continuity. 

 Partially separated cells of taste- Development. — The earliest evidences of the 



[■o^ nin-e" xTio"' m'~^'^-«^^^ taste-buds ' appear, about the third foetal month, within 



the deepest stratum of the immature epithelium as groups 

 of ectoblastic cells that are distinguished by their large size and elongated form from 

 the surrounding epithelial elements. The anlage tends to become conical, the apex 

 gradually reaching the free surface and the base resting or slightly encroaching upon 

 the subjacent connective tissue, from which it is only indistinctly defined. The 

 primary slender form of the developing bud is later replaced by one of broad conical 

 proportions in which the wide base is supported directly by the connective tissue 

 without the interposition of epithelium. 



For a time the height of the young taste-bud equals the entire thickness of the 

 epithelium, the position of its apex being marked by a slight depression on the free 

 surface. In consequence of the rapid increase of the surrounding epithelium, this 

 depression gradually deepens until the bud, which meanwhile has grown but slightly, 

 lies at the bottom of a narrow funnel-shaped passage, the pore-canal (Graberg). 

 Previous to the fifth month, the constituents of the taste-bud are apparently of 

 the same character and not until towards the end of gestation, is the differentiation 

 between the supporting and gustatory cells clearly established. The definition of 

 the taste-buds from the surrounding tissue is sharpened by the appearance of the 

 so-called cxtrabiilbar cells, flattened protecting epithelial elements in which partial 

 cornification probably takes place (Kalliusj. Coincidently many of the conical 

 embryonal buds gradually assume their more slender and ovoid mature form. Before 

 birth the taste-buds are present not only on the sides but also over the summit of 

 the circumvallate papillae. While exceptionally some of those in the latter situation 

 may remain, as a rule they disappear and, hence, in the adult the gustatory bodies 

 are usually confined to the sides of the papillae. Likewise the complement of taste- 

 buds on the fungiform papillae is much larger at birth than later (Stahr'), giving to 

 these papillae an importance during early childhood that subsequently is lost. 



THE EYE. 



Although the organ of sight (organon visus), strictly regarded, consists only of 

 the eyeball or globe of the eye, it is closely associated with other structures, as the 

 eyelids, the lachrymal apparatus, the orbital fascia and fat and the ocular muscles, 

 which serve for its protection, support and change of axis. The description of some, 

 at least, of these accessory structures therefore appropriately here finds place. 



THE ORBIT AND ITS FASCIA. 



The walls of the orbit have been described in connection with the skull (page 

 222); suffice it here to point out that in its general form the orbital cavity resembles 

 a pyramid, so modified by the rounding of its angles that it approximates an irregu- 

 lar cone. The base corresponds with the orbital opening on the face and the apex 



'Graberg : .Srhwalbe's Morpliolog. Arbeiten, Bd. viii., 1898. 

 '^Zeitschr. f. Morphol. u. Anthropol., Bd. 4, 1901. 



