DIGESTION 



The modes in which the secretion of these juices is set going have been worked 

 out almost entirely by Pavlov and his co-workers and will be found described in 

 his book (1901). When references are given to this in the following pages, it is 



to be understood that they apply to the English edition. A portrait of Pavlov 

 will be found in Fig. 98. 



It will be noticed that that method of investigation which consists in the estab- 

 lishment of openings, or fistulse, in various parts of the alimentary canal plays a 

 large part in work on the digestive processes. It is interesting to note that, so far 

 as we know, Rene de Graaf (1677) was the first to make use of this method. In 

 Fig. 99 his portrait is reproduced, There are several points of interest in the 



