ADDITIONAL ANIMAL STUDIES 189 



An examination of the skeleton of a horse (Fig. 137) or of most 

 mammals, shows that the skeleton consists of bones similar to those 

 of man. Thus, for instance, there is the spinal column made up of a 

 series of more or less similar bones, with a skull that may vary a 

 great deal in shape from that of man, but still may consist of similar 

 bones. The shoulder bones and hip bones can be readily distin- 

 guished. The bones of the legs are for the most part much alike, 

 but in the foot there is frequently a wide variation, as in the case of 

 the one-toed foot of the horse, the two-toed foot of a cow, the three 

 toes of the tapir, the four of a hippopotamus, and the five of the 

 dog or of man. 



144. Suggestions for the study of a mammal. Follow the gen- 

 eral account given above and describe the corresponding structures 

 of a horse, dog, cat, or other mammal. Thus, for instance, name 

 the regions present, and describe the character of the covering of 

 each region. Then describe the situation and parts of the eyes, the 

 situation, size, and shape of the external ears, the location of the 

 nostrils, and so on to the end of the study. Lastly, describe the 

 methods of locomotion of the animal, and its food and feeding 

 habits. 



145. Economic importance of mammals. The mammals in- 

 clude many of our most useful animals as well as those that are very 

 dangerous. Our common beasts of burden, horses and mules in this 

 country, the llama of South America, the elephant and camel of 

 Asia and Africa, are all mammals. This group of animals also fur- 

 nishes us with an immense amount of material valuable for food or 

 clothing (e.g. the cow, deer, sheep, pig, seal). The group of car- 

 nivorous mammals contains one of man's most devoted friends and 

 protectors, the dog. To the same order as the dog, however, belong 

 the wolves, lions, tigers, hyenas, and wild cats; all these have 

 canine teeth which they use with deadly effect in tearing their prey. 

 The gnawing mammals (e.g. rats and mice) besides being a nuisance, 

 do a great deal of damage. The rat also scatters diseases like 

 cholera and bubonic plague. Some rodents, the beaver, for example, 



