22 TEXTBOOK OF ZOOLOGY 



price are all orderly arranged. In this way the large unwieldy 

 number of different kinds of articles become simply managed. 



The relationships of animals are discovered from similarity of 

 structure, from facts of distribution, from embryological similari- 

 ties, and many other comparisons. A group in which the members 

 are very closely related is likely to be comparatively small. These 

 groups are ranked together according to evident relationships. 

 Zoologists recognize a number of large divisions of the animal king- 

 dom based on certain general characteristics. Each of these divi- 

 sions is known as a phylum and is divided into classes, each class 

 is divided into orders, each order into families, each family into 

 genera, and each genus into species. Taking the classification of 

 man as an example we have: 



Phylum rChordata 



Subphylum :Vertebrata 

 Class rMammalia 



Order :Primates 



Family :Hominidae 

 Genus :Homo 



Species :sapiens 



The scientific name of man is written, Homo sapiens Linnaeus. 

 Such a name is composed of the genus name and species name, and 

 followed by the name of the person who wrote the first authorita- 

 tive description of the particular species. This always gives a 

 double name to a kind of animal, and for that reason it is the 

 hinomial system of nomenclature. This system was originated by 

 Linnaeus. The names are in Latin instead of common vernacular 

 because Latin is a constant and almost universal language. The 

 common names would be almost certain to vary with each different 

 language, but the Latinized form Homo sapiens Linn, is the same in 

 Russian as it is in English. 



3. Physiology is the study of the functions of the various parts 

 of the organism as well as its living process as a whole. It involves 

 a consideration of metabolism, growth, reproduction, sensitivity, 

 and adaptation. In this field is included the study of many special 

 functions, such as digestion, circulation, respiration, excretion, 

 glandular secretion, nervous activity, muscular contraction, and 



