INTEGUMENT 27 



The integumentary glands, which are well developed in all 

 Mammals except the Cetacea, are of two kinds, hobular 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), theprepufdal glands, the inguinal 

 glands of certain Eodents, 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 Ornithorhynolius 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 



gr.m. 



Fig. 17, A. — A, Ventkal A'iew of a Be.oodin(; Fkmale of Echidna hi/th-ix. 



B, DlSSBCTIOX OF THE VeNTKAL iNTEfU'MENT FROM THE DoRSAL (IxxER) 



Side. (After W. Haacke. ) 



i', -t, the two tufts of hair in the lateral folds of the mammarj' pouch (h.m.) from 

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

 bjAStrong muscles, a group of mammary glands (,'/.»".) opens ; r/, cloaca. 



milk for the nutrition of the young. In Monotremes these 

 apparently correspond to sweat glands, while in other Mammals 

 they represent sebaceous glands. 



