100 GLANDS. 



sometimes it gives directly on the surface of the skin, 

 and when this is the case, that portion of the duct 

 which traverses the epidermis has no walls of its own 

 (fig. II 6). 



nores and ^e vascular supply of the sebaceous glands pre- 

 sents nothing peculiar, and as to their nerves we 

 know nothing of their distribution. 



Sebaceous glands are developed from the external 

 epidermic layer of the hair bulb, or rather from the 

 rete rmicosum of the epidermis. A small projection 

 buds forth, on the surface of which others, still small- 

 er, make their appearance, and these, increasing in 

 number, constitute the vesicles of the gland ; whilst 

 the base of the primitive projection, becoming more 

 elougated and constricted, forms its duct. According 

 to Valentin, the earliest rudiments of the sebaceous 

 follicles become perceptible during the last half of 

 the fourth month of foatal life. 



^ e Meibomian follicles are an aggregation of 

 minute sebaceous glands, all opening into a long, com- 

 mon, excretory duct (PL XXVII. fig. III.). 



The mammary gland, which in external appear- 

 ance resembles the salivary glands, is identical, as 

 regards its epithelium, with the sebaceous glands, at 

 least during lactation. It still more closely approxi- 

 mates to the sebaceous glands by its anatomical posi- 

 tion, and its mode of development. 



The histological elements of milk consist of simple 

 minute oil-globules, of very brilliant aspect, and dark, 

 strongly marked outlines, floating in a transparent 

 fluid (PI. XVIII. fig. VI. 4). During the first few 

 days of lactation we meet with a certain proportion 



