THE CUTIS. 



245 



Sweat-gland and the commencement of its duct : 

 a. Venous radicles on the wall of the cell in which 

 the gland rests. This vein anastomoses with 

 others in the vicinity, b. Capillaries of the gland 

 separately represented, arising from their arteries, 

 which also anastomose. The bloodvessels are all 

 situated on the outside or deep surface of the tube, 

 in contact with the basement membrane. Magn. 

 35 diam. 



and also in the neighborhood of the joints. Its amount is peculiarly great in the 

 races which are formed to inhabit warm 

 climates ; and it is probable that habitual 

 exposure of the surface generally would 

 considerably augment the quantity of 

 unctuous matter poured forth for its lubri- 

 cation. The Sudoriparous glandulae es- 

 sentially consist of long convoluted tubes 

 (Fig. 35), which, however, are rarely 

 single, but are multiplied by repeated di- 

 chotomous subdivision, sometimes also giv- 

 ing off short caecal processes before their 

 termination. These are seated rather 

 beneath the Corium, in the midst of the 

 subcutaneous adipose tissue, than in the 

 substance of the skin itself. All the tu- 

 buli of each gland unite so as to form but 

 one duct; and this passes upwards through 

 the Cutis and Cuticle, in a somewhat 

 corkscrew-like manner, to open upon the 

 surface of the latter, which it usually 

 reaches obliquely, so that the outer layer 

 of the Epidermis forms a sort of little 

 valve, which is lifted by the secreted fluid 

 as it issues forth. The Ceruminous 

 glandulae of the meatus auditorius (Fig. 

 83, c), and the Odoriferous glandulae 

 of the axilla, are mere local varieties of the ordinary sudoriparous; correspond- 

 ing with them in structure, but differing in the character of their secretion. 

 The development of all these glandulae seems, according to the observations of 

 Prof. Kolliker (Op. cit., pp. 167-172), to commence very much after the fashion 

 of that of the hair-follicles ( 247) ; namely, by a knob-like projection of the 

 deeper layer of the Epidermis, which is received into a hollow of the Cutis. 

 This gradually elongates, so as to penetrate deeper and deeper into the skin ; 

 and a cavity is formed along its axis, which, though at first destitute of an out- 

 let, gradually reaches to the surface; whilst at the same time, the deeper portion 

 becomes coiled upon itself, and the number of tubes increases by out-growth 

 from the one first formed. The secretory action of these glandulae has reference 

 rather to the wants of the economy in general, than to the special functions of 

 the skin; and it will, therefore, be more appropriately considered hereafter 

 (CHAP. xn. SECT. 4). 



239. The Cutis is very copiously supplied with Bloodvessels, which distribute 

 blood, through capillary plexuses of great minuteness, to the sweat-glands, hair- 

 follicles, and fat-clumps of its deeper portion, and then form a dense network 

 near its surface, from which looped branches are sent up into the papillae, the 

 distribution of these last being nearly the same whether the papillae are en- 

 dowed with tactile sensibility, or are subservient to the formation of the nail- 

 substance. 1 The Lymphatics of the skin, also, are very numerous, and form 

 minute plexuses near the surface. A copious supply of Nerves, too, is sent to 

 the skin ; especially to such parts of it as are thickly set with tactile papillae ; 



1 It is a curious circumstance that the under surface of the Dog's foot has a set of 

 large composite papillae, that are concerned in the formation of its thick cuticular invest- 

 ment ; which, so far as the arrangement of their vessels is concerned, closely resemble 

 those of the fungiform papillge of the tongue. 



