THE NERVOUS SYSTEM 163 



followers: In the first place, the discharge of 

 adrenaline is continuous; secondly, the amount of 

 this substance in any animal is approximately con- 

 stant ; thirdly, the supposed variation is dependent 

 on the rate at which the blood flows through the 

 veins. Keeping these views in mind, Stewart finds 

 that neither in pain, nor in asphyxia, nor in emo- 

 tional excitement, can any increased secretion of 

 adrenaline be detected. 



An experiment ~by Professor Cannon. Segments 

 of rabbit intestine were placed in cylinders and 

 these filled with samples of blood taken from the 

 lumbo- (pertaining to the loins) adrenal veins. 

 The blood was taken before and after stimulation 

 of the central end of the sciatic nerve. "Normal 

 blood removed before stimulation of the central end 

 of the sciatic nerve caused no inhibition of the 

 rhythmically contracting intestinal segment, 

 whereas that removed afterwards produced a 

 marked relaxation. 1 The conclusion was drawn 



a ln the chapter on the adrenal glands we stated that there 

 were two accepted methods for the estimation of adrenaline, 

 the one a physiological, and the other a chemical method. The 

 physiological method is the more sensitive, and for the extremely 

 minute quantities of the substance with which we are here deal- 

 ing, the physiological method is, at present, the only one that 

 yields results. The principle employed is one -which depends 

 upon the fact that a portion of an organ, such as the uterus or 

 the intestine, when bathed in blood or in Ringer's solution 

 containing a mixture of inorganic salts of a concentration similar 

 to that found in blood will produce rhythmic contractions that 

 can be made to record on a slowly revolving drum; when, how- 

 ever, adrenaline even in the proportion of onpart in one million 



