VELOCITY OF REACTIONS 23 



that the method of working in the organism differs 

 from that used in the chemical laboratory. This 

 question is of a much more recent date than that 

 mentioned above, because the progress of chemical 

 processes has not been thoroughly investigated 

 before the last great development of physical 

 chemistry. Therefore our chief task will be to see 

 if the physico-chemical laws regarding the progress 

 of chemical processes in general chemistry are also 

 applicable to biochemical processes, and we shall 

 especially try to elucidate such biochemical processes 

 as have been considered exceptions from known 

 physico-chemical laws. 



In this case we have not only to regard the 

 processes going on in the living organism, for these 

 are in most cases verydifficult to examine thoroughly, 

 but also to investigate chemical processes, char- 

 acteristic of organic products which react upon each 

 other outside of the living body, or, as it is called, 

 "in vitro" (in a glass vessel). As far as is known, 

 biochemical processes develop in the same manner 

 in the living body, "in vivo," as "in vitro" if the 

 same reagents are used under the same circum- 

 stances. Without the aid of experiments " in vitro " 

 we should really know very little of the much less 

 accessible reactions " in vivo." The characteristic 

 feature of these reactions is that they are bound up 

 with the action of certain organic products, which 

 have not so far been produced synthetically, because 

 they occur in such small proportions, and are so 

 difficult to isolate from other organic products, that 



