MAMMALS OF MINNESOTA. 13 
CHAPTER I. 

hea r The first question which we encounter is ‘‘What is a mam- 
- mal?” Every one is practically familiar with a greater or less 
number of mammals, and is possessed of a more or less dis- 
- tinct notion of the points of similarity and diversity between 
i such of these animals as are most familiar, but it may be sus- 
pected that such of my readers as are not themselves natural- 
‘ists may not be prepared to state the distinctions which sepa- 
ratemammals from all other animals. It isremarkable how 
_ few ideas are united in the popular conception represented for 
example by the words cow, dog, cat, etc. We may perhaps think 
of a cow as an ungainly quadruped with hoofs and horns, which 
occupies herself in chewing a cud and brewing milk. One 
familiar with country life will be likely to add that the hoofs 
ee ‘of a cow are divided and the horns are furnished with a core 
of bone and not, like those of an elk, solid and deciduous and, 
perhaps, that there are certain peculiarities in the dentition. 
_A keen observer would recall that there are really four hoofs 
which represent four toes on each foot, that the stomach is 
curiously differentiated and thus exhaust what are popularly 
- considered the distinctive features of a bovine. So able a 
) writer as John Fiske speaks of a ‘‘hoof as made up of five 
claws grown together and furnished with a nail in common.”’ 
_ (The Destiny of Man, p. 36). Yet few wouldever have thought 
__ to inquire which of all these points does a cow have in common 
A with a mouse, a kangaroo or an elephant, which animals are as 
truly mammals as the cow or her master. 
; The mammals are members of the sub-kingdom Vertebrata 
i ; among the prominent characters of which are the following: 
The body is composed of two cavities of unequal size, the 
uppermost of which contains the central part of the nervous 
“system, or, in other words the brain and spinal cord, while the 
_ lower cavity contains the viscera. The nervous cavity is separ- 
ated from the visceral by a chain of bones which usually also 
‘sends up bony walls which completely enclose the organs 
contained init. The anterior portion of the nervous system or 
- brain is usually highly developed and encased in a complicated 



