Fes., 1912. Mammats or ILLINoIs AND WIscoNnsIN — 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 vibrisse (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. 
