776 REPORT— 1902. 



part played by bold theorising, tbe work of Pawlow that played by the introduc- 

 tion of new and bold methods of experiment. 



I will take Pawlow first. This energetic and original Russian physiologist has 

 by his new methods succeeded in throwing an entirely new light on the processes 

 of digestion. Ingeniously devised surgical operations have enabled him to obtain 

 the various digestive juices in a state of absolute purity and in large quantity. 

 Their composition and their actions on the various foodstuffs have thus been ascer- 

 tained in a manner never before accomplished ; an apparently unfailing resource- 

 fulness in devising and adapting experimental methods has enabled him and his 

 fellow workers to discover the paths of the various nerve impulses by which secre- 

 tion in the alimentary canal is regulated and controlled. The importance of the 

 psychical element in the process of digestion has been experimentally verified. If 

 I were asked to point out what I considered to be the most important outcome of 

 all this painstaking work, I should begin my answer by a number of negatives, and 

 would say, not the discovery of the secretory nerves of the stomach or pancreas ; 

 not the correct analysis of the gastric juice, nor the fact that the intestinal juice 

 has most useful digestive functions; all of these are discoveries of which anyone 

 might have been rightly proud ; but after all they are more or less isolated facts. 

 The main thing that Pawlow has shown is that digestion is not a succession of 

 isolated acts, but each one is related to its predecessor and to that which follows 

 it ; the process of digestion is thus a continuous whole ; for example, the acidity 

 of the gastric juice provides for a delivery of pancreatic juice in proper quantity 

 into the intestine ; the intestinal juice acts upon the pancreatic, and so enables the 

 latter to perform its powerful actions. I am afraid this example, as I have tersely 

 stated it, presents the subject rather inadequately, but it will serve to show what 

 I mean. Further, the composition of the various juices is admirably adjusted to 

 the needs of the organism ; when there is much proteid to be digested, the proteo- 

 lytic activity ofthe juices secreted is correspondinglj' high, and the same is true for 

 the other constituents of the food. It is such general conclusions as these, the cor- 

 relation of isolated facts leading to the formulation of the law that the digestive 

 process is continuous in the sense I have indicated and adapted to the needs of the 

 work to be done, that constitute the great value of the work from the Russian 

 laboratory. Work of this sort is sure to stimulate others to fill in the gaps and 

 complete the picture, and already has borne fruit in this direction. It has, for 

 instance, in Starling's hands led to the discovery of a chemical stimulus to pan- 

 creatic secretion. This is formed in the intestine as the result of the action of the 

 gastric acid, and taken by the blood-stream to the pancreas. Whether this secretin 

 as it is called may be one of a group of similar chemical stimuli which operate in 

 other parts of the body has still to be found out. 



The other series of researches to which I referred are those of Ehrlich and his 

 colleagues and followers on the subject of immunity. This subject is one of such 

 importance to every one of us that I am inclined to place the discovery on a level 

 with those great discoveries of natural laws to which I alluded at the outset of 

 this portion of my Address. I hesitate to do so yet because many of the details 

 of the theory still await verification. But up to the present all is working in that 

 direction, and Ehrlich's ideas illustrate the value of bold theorising in the hands of 

 clear-sighted and far-seeing individuals. 



But when I say that the doctrine is bold, I do not mean to infer that the 

 experimental facts are scanty ; they are just the reverse. But in the same way 

 that a chemist has never seen an atom, and yet he believes atoms exist, so no one 

 has yet ever seen a toxin or antitoxin in a state of purity, and yet we know they 

 exist, and this knowledge promises to be of incalculable benefit to suffering 

 humanity. 



It may not be uninteresting to state briefly, for the benefit of those to whom 

 the subject is new, the main facts and an outline of the theory which is based 

 upon them. 



We are all aware that one attack of many infective maladies protects us 

 against another attack of the same disease. The person is said to be immune 

 either partially or completely against that disease. Vaccination produces in a 



