Mechanistic Biology 233 



written years before the dispute became general. To deny the 

 action of the soul upon the body, he said, was 



" To devolve the honour of the principal agent upon the 

 instrument, which, if with reason we may do, then let our hammers 

 rise up and boast that they have built our houses, and our pens 

 receive the honour of our writings." 



Experimental researches during this period were not wanting, 

 and they all tended in a mechanistic direction, though this was not 

 understood at the time. Reaumur in 1752 was the first to study 

 enzymes from the digestive juices outside the body and to show 

 that the processes of life possessed a definite optimum temperature. 

 But the eighteenth century closed with the general acceptance of 

 a mild vitalism, represented by Bichat and Johannes Miiller. It 

 was the calm before the storm. As soon as the nineteenth century 

 had begun steadily and without intermission the tide of mechanistic 

 interpretations in biology went forward. The two most important 

 dates in this period are 1828 and 1897, and they are indeed of 

 enormous significance. In 1828 Wohler carried out at Giessen 

 the synthesis of urea in the laboratory. Before that time it had 

 been generally accepted even among the vitalists that the animal 

 organism was constituted out of the same elements and compounds 

 as those of inorganic nature — though it had required much work 

 on the part of the famous biochemist, Justus von Liebig, himself 

 a vitalist, to convince them of that. At the same time it was 

 generally felt that though the chemical elements inside and outside 

 the animal body might be the same, yet the compounds found in 

 the body could only be manufactured by the body. Such a sub- 

 stance as urea or uric acid, they thought, though capable of ordinary 

 chemical analysis, could never be produced without the interven- 

 tion of life in some form or other, because for its making vital force 

 was necessary. This whole conception was shattered by Wohler's 

 synthesis of urea from inorganic substances in the laboratory, for 

 what could be done once could be done again, and all the con- 

 stituents of the animal body must one day be capable of synthesis 

 in the laboratory. No vital force was necessary. The vitalists 

 had to retire from that position. 



But they still possessed the stronghold of the view that the 

 organism is not subject to the laws of thermodynamics. All 

 through the middle part of the century argument was conducted 



