THE METABOLISM OF THE BODY. 



433 



diet. Even bees can construct their wax from proteid, or use 

 unlike substances, as sealing-wax. 



n.m.d 



Fig. 324.— Section of mamma^ gland (udder and nipple) of cow (after Thanhoffer). 

 Ma, substance of gland; N nipple; A, acini of gland; m. d, milk-ducts; C, milk- 

 cisterns; /, folds in wide milk-dncts; S, section of sphincter muscle; e, external 

 skin; n. m. d, narrow milk-duct in nipple. 



But histological examination of foijming adipose tissue itself 

 throws much light upon the subject. Fat-cells are those in 

 which the protoplasm has been largely replaced by fat. The 

 28 



