DISSIMILATION 



95 



surrounded by capillaries and ending in a cup containing a knot of 

 small arteries (Fig. 31, p. 53). Evidence as to the function of the 

 various parts of the tube with reference to the ehmination is con- 

 flicting, and final conclusions have not been reached. Some hold 

 that, from the glomerulus, water and inorganic salts filter through 



Epidennia 



Dermis 



Adipose tissue 



Fig. 52. — Diagram of section through the skin of man showing characteristic 



structures. 



B, biilb or root of h.air, where growth occurs; C.N., capillary net surrounding sweat 

 gland; D, dui't of sweat gland; M, erector muscle of hair; P, papilla of hair, where blood 

 vessels and nerve endings associated with hair are found; S, shaft of hair which extends 

 beyond surface of skin; Sb.G., sebaceous or oil gland from which secretion passes to the 

 surface by way of the hair follicle; Sw.G., sweat gland from which perspiration is eliminated. 



Bowman's capsule, and that the nitrogenous compounds are 

 passed in through the walls of the convoluted tubules. An older 

 view was that all the constituents were filtered out at the glomerulus 

 and that some water was reabsorbed from the tubule. Here again, 

 the physical factors governing the passage of materials through 

 living cells are not completely understood. 



