610 MANUAL OF HISTOLOGY. 



nective-tissue. As a rule we find no blood-vessels about the body of the 

 gland. The process of secretion in the latter appears to be of a very low 

 order, but active enough to meet all the functional requirements of the 

 organ, which is designed to communicate to the hairs and surface of the 

 skin a certain slight degree of oiliness. 



The secretion itself, sebum cutaneum, when fresh, is a thickish oily sub- 

 stance, which stiffens after some time like lard which has been heated. 

 Its form-elements (B), found together with cast-off epidermal scales in 

 variable amount, have been described at p. 352. Chemically the mass 

 consists apart from slight differences dependent on locality of a large 

 proportion of neutral fats in addition to soapy materials, cholestearin, and 

 a protein substance. Among its inorganic constituents the chlorides and 

 phosphates of the alkalies appear in small proportion, but the earthy 

 phosphates in considerable amount. 



The development of the sebaceous follicles takes place from the external 

 cell-layer of the skin like the sudorific and mammary glands ; it is, how- 

 ever, usually linked with that of the first rudiments of the hairs, and 

 may be remarked in the fourth or fifth month of foetal existence. 



At first these glands present themselves in the form of solid buds on 

 the rudimentary external root sheaths (p. 390), primarily of globular 

 figure, and subsequently flask -like. These buds are produced by prolifera- 

 tion of the formative cells of that sheath ju^t mentioned. As Koelliker 

 has pointed out, there very soon commences in the axis of this simply 

 formed sebaceous gland a fatty degeneration of its contents, so that the 

 little organ, even at this early period, already exhibits the characteristic 

 features of its secretory process. 



The further changes destined to convert this simple flask-shaped sac 

 into a plain or complicated racemose gland begin, on the other hand, at a 

 comparatively late period, namely, in the later months of intrauterine 

 life. They depend upon a multiplication of the peripheral cells causing 

 new gemmation at the surface, a process which is not completed at the 

 time of birth, and by the continuation of which the complicated lobulated 

 form' of many of the sebaceous glands is gradually perfected. 



REMARKS. (1.) Todd and Bowmann, vol. i. p. 424. 



305. 



As regards the mode of termination of the (justatory nerves of the tongue 

 our knowledge is still scanty and unsatisfactory. The organ itself has 

 been considered at greater length in speaking of the digestive apparatus 

 ( 247, 248). Much advance, however, has been made of late years in 

 increasing our stock of facts relating to this question. 



In the circumvallate papillae of the human and mammalian tongue, 

 peculiar terminal apparatuses were discovered almost at the same time, 

 and independently of one another, by Loven and Schwalbe, for which the 

 name of " gustatory buds" chosen by the first of these observers, recom- 

 mends itself most. The term " taste-cups" proposed by Schultze, appears 

 less suitable. Here, again, Engelmann and Wyss both found, indepen- 

 dently of each other, an analogous gustatory organ on the side of the root 

 of the tongue in the rabbit, a plicated body presenting similar " gustatory 

 buds'" represented in our woodcut. This is known as the " papilla 

 foliata." 



These papillae foliatae also occur in the human tongue. They are seated 

 immediately before the bases of the pillars of the arcus glossopalatinus, 



