INTEGUMENT 



27 



The integumentaiy glands, which are well developed in all 

 Mammals except the Cetacea, are of two kinds, tubular and acinous. 

 The former include the siveat-glands and their various modifica- 

 tions ; while the latter are spoken of as sebaceous glands, and include 

 the already-mentioned glands of the hair-sacs, which serve to oil the 

 hair (Figs. 15 D, and 16, A and B), the preputial glands, the inguinal 

 glands of certain Rodents, the Meibomian glands of the eyelids, and 

 many others. It must be borne in mind, however, that there is 

 not always a sharp distinction between these two kinds of glands. 



The paired femoral gland of Ornithorhynchus opens by means of a long 

 duct on to the spur present on the hind foot. Its secretion is poisonous. 



Another important modification of the integumentary glands 

 of the Mammalia is seen in the mammary glands, which secrete 



A B 



g.m 



FIG. 17, A. A, VENTRAL VIEW OF A BROODING FEMALE OF Echidna hystrix. 

 B, DISSECTION OF THE VENTRAL INTEGUMENT FROM THE DORSAL (INNER) 

 SIDE. (After W. Haacke.) 



t, : f, the two tufts of hair in the lateral folds of the mammary pouch (b,m.) from 

 which the secretion flows. On either side of the pouch, which is surrounded 

 by* strong muscles, a group of mammary glands (g.m.) opens ; cl, cloaca. 



milk for the nutrition of the young. In Monotremes these 

 apparently correspond to sweat glands, while in other Mammals 

 they represent sebaceous glands. 



g. m. 



