112 INFLUENCE OF CENTRAL NERVOUS SYSTEM 



diphtheria toxin than the rabbit because in the guinea-pig 

 the non-fatal dose of this toxin is completely fixed and 

 retained by the cellular tissue and never produces nervous 

 crises; in the rabbit the same toxin is not retained by cellu- 

 lar tissue and always paralyzes. But in attempting to 

 immunize these two animals against tetanus toxin the 

 reactions and results are exactly reversed. It is thus very 

 probable that in these two cases the production of anti- 

 bodies is, in a certain measure, modified by the influence of 

 the central nervous system. 



We may quote here the experiences of Kendall 1 on the 

 action in vitro of suprarenal cortex on ammonium carbo- 

 nate. This action is very different according to whether 

 the operation for the removal of the cortex is done in an 

 animal normally sluggish without having undergone any 

 nervous excitement or whether in an animal recently and 

 violently frightened. In the first case the ammonium car- 

 bonate undergoes no modification; in the second, it is trans- 

 formed into a poorly defined substance which Kendall has 

 called pre-urea because when excreted in urine it is trans- 

 formed into urea. 



The researches of Cannon 2 demonstrate beautifully the 

 actual physiological changes brought about by the central 

 nervous system. Cannon showed that after any violent 

 emotion, such as fear or rage, there is a marked liberation 

 of "epinephrin" from the suprarenal cortex and a liberation 

 of glycogen from the liver. This sudden liberation of epi- 

 nephrin, which takes place in a matter of seconds, causes 

 in turn the production of many and varied disturbances in 

 the organism such as stimulation of the sympathetic nerves, 

 increase in the blood coagulability and in the relative pro- 

 portion of red blood cells. 



Psychic excitations can thus produce a proved modifica- 

 tion in metabolism and resulting from this a change not 

 only in the substances contained in the suprarenal cortex 

 but in the quantities of substances secreted. 



1 Experimental Hyperthyroidism, Jour. Am. Med. Assn., 1917, Ixix, 610. 



2 Am. Jour. Physiol., 1915-16, vols. xl-xlii. 



