BREASTS AND MILK. 379 



gliinds forms in this way the most simple type of moulting 

 of the globules. 



Two-thirds of the sebaceous matter thus produced consists 

 of water, the rest being chiefly fats, some extractive and 

 albuminous substances, and some earthy salts. The fatty 

 substances are the most important in a physiological point of 

 view. It is owing to these latter that the sebaceous matter 

 possesses the property of imparting a certain quantity of 

 grease to the hair, and of imparting an oily feeling to the 

 whole surface of the epidermis, thus increasing its impermea- 

 bility. Whatever may be the varieties in form and arrange- 

 ment of the sebaceous glands, their use is always the same; 

 the purpose of the meibornian glands, which are elongated 

 sebaceous glands situated in the eyelids, is to anoint, their 

 free edge, and thus prevent the product of the lachrymal 

 gland from overflowing on to the cheeks. 



We have already seen that the tonsil (see p. 280) may be 

 described as a complex sebaceous organ, developed from a 

 mucous gland, and connected, at its base, with the lymphoid 

 follicles : this tonsil likewise produces a sebaceous matter the 

 use of which is not fully known. 



It frequently happens that the secretory globules of the 

 sebaceous glands do not attain their maturity in a regular 

 manner; being imperfectly dissolved, the sebaceous matter 

 remains in the state of desquamated epithelium, instead of 

 becoming an oil or half-liquid fat ; it no longer flows easily, 

 and its accumulation in and dilatation of the glandular sac 

 produces sebaceous cysts or wens, which grow sometimes to an 

 enormous size. Large quantities of fatty substances are found 

 in these cavities, as well as a surprising proportion of crystal- 

 lized cholesterine. (In a cyst of this sort, containing 2 kilos, 

 of sebaceous matter, 15 grms. of cholesterine were found.) 



3. Breasts and Milk. The mammary gland (Fig. 99) 

 consists of a union of from 15 to 20 highly developed seba- 

 ceous glands ; the glands of the scrotum and of the fold of 

 the groin sometimes furnish a product closely resembling 

 milk ; in the areola of the nipple are found immense seba- 

 ceous glands, called erratic lacteal glands, which exactly fol- 

 low the variations in development of the mammary gland, 

 going through the processes of atrophy and hypertrophy in 

 the same manner. 



The numerous culs-de-sac of the sebaceous glands, which 

 culminate in lacteal glands, unite to form the 15 or 20 tubes 

 leading upwards to the nipple, where they open into as many 



