HISTORICAL ZOOLOGY 



273 



anatomy, and, in his Elements of Physiology (1758), summed up 

 the principal facts and theories of his predecessors. Johannes 

 Muller (Fig. 155) founded modern comparative physiology, and 

 prepared a handbook of the physiology of man, based upon the 

 personally verified statements of others and upon his own obser- 

 vations, which to this day has no equal. He made use of the 

 microscope, and brought to his work a knowledge of physics, 

 chemistry, and psychology. Since his time physiological in- 

 vestigations have progressed along physical and chemical lines, 

 and vital activities are now explained by many in physico- 

 chemical terms. 



/. Evolutionary Zoology 



It is difficult in this place to give an adequate history of evolu- 

 tionary zoology without discussing the evolution theory in 

 detail. We shall, however, leave that for the succeeding chap- 

 ter, and restrict ourselves to a brief account of the work of a very 

 few men who have accomplished the most in this field. Lamarck 

 (1774-1829) was one of the first to recognize the instability of 

 species, and was the first to make use of a genealogical tree to 

 show the relationships of animals. His most important work is 

 entitled Philosophic Zoologique, published in 1809. It contains 

 statements of his belief in the inheritance of acquired characters, 

 the result of use and disuse, and other less important views. 



But the greatest of all scientists who influence our evolutionary 

 ideas was Charles Darwin (1809-1882, Fig. 156). His book on 

 the origin of species, published in 1859, changed the trend of 

 investigations in many fields of science, and did more than any 

 other factor to place evolution upon a firm foundation. At the 

 present time organic evolution, or the transmutation of species, 

 is accepted by practically every well-known zoologist, and our 

 attention is directed toward the problem of the method by which 

 evolution takes place. , Darwin's theories have been assailed 

 frequently, and are no more accepted by many zoologists in 



