334 MAMMALS 



The gorilla is the largest of the manlike apes, often reach- 

 ing a height of five feet, four or six inches. It lives in deep 

 forests, in a very restricted portion of western Africa in the 

 Congo district. Its forehead retreats strongly, its expres- 

 sion is brutal, and the body is more uniformly covered with 

 hair than that of the chimpanzee. The gorilla naturally 

 walks on all fours, but it can walk erect although rather 

 clumsily. Its ferocity has been exaggerated. 



Man. — As an animal, man belongs to the family Homin- 

 idse and is known scientifically as Homo sapiens. As an 

 animal, he is distinguished for his erect posture, very com- 

 plete opposition of the thumb to the fingers, short canine 

 teeth, greater length of hind, as compared with fore limbs, 

 and the great size and complexity of the brain. 



Characteristics of the mammals. — As we have already 

 learned, the name of the class is derived from the fact that 

 the young are nourished for a longer or shorter time on milk, 

 which is a fluid secretion from certain specialized glands 

 known as mammee. Secondly, it may be said that the 

 bodies of mammals, at some period of their existence, are 

 more or less covered with hair. We have seen from our own 

 study and observation that many are completely covered 

 with hair, except the nose and soles of the feet. On the 

 other hand, the whales are wholly destitute of hair, or very 

 sparsely clothed with it, in the adult stage ; but it is present 

 on portions of the body in embryonic whales. Moreover, 

 the heart, as in birds, consists of four chambers, the two 

 on one side being completely separated from the two on the 

 other side. Hence, there is a double circulation. The 

 thorax is separated from the abdomen by a strong muscular 

 partition known as the diaphragm. This aids greatly in 

 respiration. The mammals, in general, bring forth their 



