FEB., 1912. MAMMALS OF ILLINOIS AND WISCONSIN CORY. 19 



naturally white, and these are largely restricted to boreal species, 

 although there are a number of exceptions including a white Bat 

 which occurs in South America. While in some cases, such as the 

 tail of a Horse, the hairs appear to be permanent, as a rule they are 

 periodically shed and replaced by a new growth. In the majority 

 of mammals the color of the new hair differs but little and the 

 change in appearance of the animal is comparatively slight; but in 

 some species, like our Weasels and Varying Hare, there is a complete 

 semiannual change of color in some localities. In some mammals 

 the long bristley hairs or vibrissa (commonly called whiskers) , which 

 extend from the side of the face, are connected with exceedingly 

 sensitive nerves and perform a sensory function. These, however, 

 will be referred to again under the organs of sense. 

 Odor-secreting Glands In many mammals there are present integu- 

 mental glands located in various parts of the body, the secretions of 

 which serve to attract others of their kind, and in a number of cases 

 their functions seem to be two-fold, as they furnish a means of 

 defense against their enemies as well. The Skunk may be cited as 

 one of the best known examples of the latter class, on account of its 

 well-known ability to eject by muscular contraction, a noxious 

 smelling liquid for a considerable distance. In a large number of 

 mammals possessing glands of this character the secretions are 

 characterized by their musky odor and are variable in intensity, 

 many of them being comparatively inoffensive. In some cases 

 these glands are developed in the male only, but in others they are 

 present in both sexes. 



As illustrating the diversity of location of this group of structures 

 in various species, we may mention the anal glands of various 

 Carnivores, such as the Skunks, Wolverines, etc., the preputial 

 glands of the Musk Deer and Beaver, dorsal glands of the Peccary, 

 foot gland of the Rhinoceros, and those between the toes of many 

 of the Ruminants, the suborbital glands of the Antelope, temporal 

 gland of the Elephant, caudal gland of the Dog, Fox, etc., and the 

 variously situated glands of Bats, Shrews, Mice, and many others. 



CIRCULATORY AND DIGESTIVE SYSTEMS. 

 The body cavity of a mammal is divided into two sections separated 

 by a muscular diaphragm. The upper or plural cavity contains the 

 heart and lungs, while the lower or peritoneal cavity contains the 

 stomach, intestines, liver, etc. Of these organs I shall briefly discuss 

 those which will be referred to later in connection with the various 

 families included in this work. 



