THE GROWTH AND SCOPE OF BIOLOGY 



Besides correcting an ancient mistake, Harvey performed a service to 

 biology in making it an experimental science. While others before 

 Harvey had occasionally used experiments, he gave the method a strong 

 impetus. But while Harvey was modern in his method of solving 

 problems, at the same time his concept of life and its manifestations in 

 general was no more advanced than was that of Aristotle. 



The Seventeenth and Eighteenth Centuries. — The two centuries 

 following Harvey mark a distinct phase in the development of biology. 

 The lethargy of the Middle Ages had been definitely cast off, and the 

 spirit of inquiry was again prevalent among intelligent people. Two 



Fig. 5. — Two early microscopes. Left, that used by Robert Hooke; right, from eight- 

 eenth century. (From "Educational Focus," Bausch & Lomb Optical Co., and American 

 Museum, of Natural History.) 



general concepts of natural phenomena arose, one of them mechanistic, 

 the other mystical ; and the history of biology ever since has been in part a 

 conflict between these two systems of thought, with the former steadily 

 gaining ground. The science of chemistry was coming to the aid of 

 biology by enabling physiology to seek for purely mechanistic explana- 

 tions of life processes. Following Harvey's proof of the circulation came 

 the dicovery of the lymphatic system of vessels carrying digested food 

 from the intestines to one of the larger veins. The nervous system was 

 more thoroughly studied, and the functions of the divisions of the brain 

 began to be understood. The contraction of muscles was explained by 

 fermentation — incorrectly, but it is significant that the role of chemistry 

 in living matter was recognized. However, the early advances were 

 mostly in the field of morpholog}'', the science of structure. 



