MECHANICAL PHENOMENA. 7 



volume do not allow even an outline of the various views 

 which have been held from time to time. Many of these 

 we now know to be entirely false, others in part, often in 

 large part, correct. 



Within recent years a number of papers have appeared 

 on the movements of the gastro-intestinal tract which have 

 given us a clearer insight into this problem. Foremost 

 among these newer researches stand the observations of 

 CANNON in this country and Roux and BATHAZARD in 

 France. The observations of these men are free from many 

 of the objections which may be lodged against the older 

 studies of the subject. 



Experiments in mammalian physiology must of necessity 

 be so often carried on under anaesthetics or the disturbing 

 influence of operative procedures that when these factors 

 affect the physiological process which is being investigated 

 results are obtained which if not wrong are at least con- 

 fusing. It is ta the disturbing influences of the methods 

 used in the investigation of the movements of the gastro- 

 intestinal tract by the older observers that some of their 

 confusing results are to be attributed, and it is but natural 

 that the introduction of experiments in which all operative 

 interference, anaesthetics, etc., are shut out should yield 

 more trustworthy results than our older ones; while they 

 indicate to us at tone same time what is right and whaf is 

 wrong in our oldeMconceptions. 



CANNON and Roux and BATHAZARD used the x-ray in 

 their study of the .movements of the alimentary tract. This 

 does away with tne necessity of surgical operations in order 

 to obtain a view of the intestines, and at the same time 

 prevents the exposure of the abdominal contents to the cold 

 cf the air, to evaporation, etc., all of them important factors 

 in modifying the normal activity of the hollow viscera. 

 In order to render the food visible within the alimentary 

 tract, bismuth subnitrate was mixed with it. Since this 

 substance is opaque to the x-rays, the food may readily be 



