MAN'S PLAG& AMONG VERTEBRATES. l\ 



Man's place among Vertebrates. It must be clear to 

 every one that although man's structural plan in its broad 

 features, simply indicates that he is a vertebrate animal, 

 yet he is much more like some vertebrates than others. 

 The hair covering more or less of his body, and the organs 

 which produce milk for the nourishment of the infant by 

 its mother, are absent entirely in fishes, reptiles, and birds, 

 but are possessed by ordinary four-footed beasts and by 

 whales, bats, and monkeys. The organs which form milk 

 are the mammary glands, and all kinds of animals whose 

 females possess them are known as Mammalia *: man is. 

 therefore, a Mammal. In internal structure one of the 

 most important characters of the Mammalia is the pres- 

 ence of a cross-partition, called the midriff or dia- 

 phragm, which separates the haemal cavity into an an- 

 terior and a posterior division. This partition is shown at 

 d in Fjg. 1, where it is seen to divide the ventral cavity 

 into an upper and a lower story ; the upper or anterior is 

 the chest or thorax cavity j the lower or posterior, the 

 abdominal cavity. The chest contains the heart, lungs, 

 and most of the gullet ; the abdomen contains the lower 



In what external characters does the human body differ from 

 that of fishes, reptiles, and birds? Name some animals which agree 

 with mankind in the possession of these characters ? What are 

 the mammary glands? What is meant by Mammalia? To what di- 

 vision of vertebrate animals does man belong? 



Point out a fact in internal structure in which the Mammalia 

 differ from other vertebrates? Where does the diaphragm lie? What 

 is the name of the cavity above it? What is the name of the cavity 

 below it? Name some organs lying in the thorax. Some placed in 

 the abdomen. Some which run through both. 



* Zoologists classify vertebrate animals in five groups. 1. Pisces, including all 

 true fishes, as sharks, eels, salmons, shad, perch, &c., but excluding the so-called 

 shellfish, as oysters, clams, and lobsters, which are not vertebrates at all. 2. Am- 

 phibia, frogs, toads, newts, salamanders &c. 3. EeptUia, lizards, alligators, turtles, 

 snakes. 4. Aves, birds. 5. Mammalia. 



