12 CIVET AND MUSK 



their darker coat in the spring. This is, however, only an 

 extreme case of a change which is general. Most animals get 

 a thicker fur in winter and exchange it for a lighter one in 

 summer. And the hues of the coat change in correspondence. 



Glands of the Skin. — The great variety of integumental 

 glands possessed by the Mammalia distinguishes them from any 

 group of lower Vertebrates. This variability, however, only con- 

 cerns the anatomical structure of tlie glands in question. Histo- 

 logically they are all of them apparently to be referred to one of 

 two types, the sudoriparous or sweat gland and the sel»aceous 

 gland. Simple sweat and sebaceous glands are abundant in 

 mammals, with but a few exceptions. The structures that we are 

 now concerned with are agglomerations of these glands. The 

 mammary glands will l)e treated of in connexion with the mar- 

 supium ; they are eitlier masses of sweat glands, or of sebaceous 

 glands whose secretion has been converted into milk. 



Many Carnivora possess glands opening to the exterior, near 

 the anus, hj a large orifice. These secrete various odoriferous 

 substances, of which the well-known " civet " is an example. 

 Otlier odoriferous glands are the musk glands of the Musk-deer 

 and of the Beaver ; the suborl)ital gland of many Antelopes ; the 

 dorsal gland of the Peccary, which has given the name of 

 Dicofi/Irs to the genus on account of its reseml)lance in form to 

 a navel. This gland may l)e seen to secrete a clear w^atery fluid. 

 The Elephant has a gland situated on the temple, which is said 

 to secrete during certain periods only, and to be a warning to 

 leave the animal alone. Very remarkable are the foot glands <~>f 

 certain species of BMnoceros ; they are not universally present 

 in those animals, and are therefore useful as specific distinctions. 

 On the back of the root of the tail in many Dogs are similar 

 glands. The Gentle Lemur {Ha^ialemur) has a peculiar gland 

 upon the arm, a]»out the size of an almond, which in the male 

 underlies a patch of spiny outgrowths. In Lemvr varius is a 

 hard patch of black skin which may be the remnants of such 

 a gland. Tt is thought that the callosities on the legs of Horses 

 and Asses are renmants of glands. 



One of the most comx)lex of these structures whicli has lieen 

 examined microscopically exists in the Marsupial Miirmecohius} 

 On the skin of the anterior part of the chest, just in front of the 

 ' Proc. Zool. Sne. 1887, p. 527. 



