INTROD UCTION. S 



summation of most complicated vital processes, the ex- 

 planation of the organic bodily form is, therefore, in 

 ultimate analysis a physiological problem ; though of 

 course a problem whose solution lies still in the indefi- 

 nitely distant future. What has been actually accom- 

 plished in this direction is only the smallest beginning, 

 even in comparison with that which many falsely regard as 

 already attained. 



Biology. According as the relations of each organism 

 to the external world are brought about through its vital 

 phenomena, there belongs to Physiology, or at least is - 

 connected with it, the study of the conditions of animal 

 existence, Oncology or Biology. This branch of the science 

 has of late attained a very considerable importance. How 

 animals are distributed over the globe, how climate and 

 the configuration of the earth's surface influence their dis- 

 tribution, how by known factors the structure and the 

 mode of life become changed, are questions which are 

 to-day discussed more than ever before. 



Paleontology. Finally in the realm of Zoology belongs 

 also Palcozoology or Paleontology, the study of the extinct 

 animals. For between the extinct and the living animals 

 there exists a genetic relationship: the former are the 

 precursors of the latter, and their fossil remains are the 

 most trustworthy records of the history of the race, or 

 Phvlogcny. As in human affairs the present conditions can 

 only be completely understood by the aid of History, so 

 in many cases the zoologist must draw upon the results of 

 Paleontology for an explanation of the living animal 

 world. 



The science of Zoology would be subdivided in the 

 above-mentioned manner if we wished to proceed entirely 

 on a scientific basis. Yet practical considerations have 

 made necessary many modifications. On account of their 

 paramount importance to the medical profession Human 

 Anatomy and Embryology have been raised to inde- 

 pendent branches of science. In Animal Physiology only 

 the most general foundations have been laid ; a more 



