126 THE PHILOSOPHY OF BIOLOGY 



were sufficient in themselves without the mystical 

 " sensitive soul " and " archei." With Sylvius and 

 Mayow physiology became based upon chemical dis- 

 covery and again became mechanistic, and remained 

 so until the time of Stahl, when chemical discovery 

 attained for the time its greatest development. 



The seventeenth century ended with the work of 

 Stahl. It is well known to students of science how 

 the views of this great chemist sterilised chemical 

 investigation almost until the time of Lavoisier. The 

 notion of phlogiston as an active constituent of material 

 bodies entering and leaving them in their reactions with 

 each other was a clear and simple one, and it served as 

 a working hypothesis for the chemists who immediately 

 followed Stahl. It was, of course, a false hypothesis, 

 and retarded discovery to the extent that the greater 

 part of the eighteenth century is a blank for chemistry, 

 when compared with the seventeenth and nineteenth 

 centuries. Deprived therefore of the stimulus afforded 

 by new physico-chemical methods of investigation, 

 physiology ceased to maintain the progress it had 

 made during the previous century, and the only great 

 name of this period is that of von Haller. Comparative 

 anatomy, and zoological exploration, on the other 

 hand, made enormous advances, and for these branches 

 of biology the eighteenth century was the great 

 period. It was the period of the historic vitalistic 

 views — vital principles, and vital and formative forces. 

 Stahl's teaching dominated physiology just as it did 

 chemistry. Chemical and physical reactions occurred 

 in the living body just as they did in non-living matter, 

 but they were controlled and modified by the soul, or 

 vital principle. It has been said that Stahl's vitalistic 

 teaching retarded the progress of physiology, but it 

 does not seem clear that this was the case. What did 



