NOTE ON CHEMICAL STIMUL1 IN REGARD TO CONTRACTION ECC. 459 



is ioiperfectly known and the modo of disappearance is also 

 unknown. It is not certain that the amo un t can be easily 

 influenced. One does knovv, and the Cambridge Committee 

 proved that the consumption of oxygen is diminished by the 

 use of some substances, and increased by others. Lactic acid 

 seems to be a bye product. We learn from chemical obser- 

 vations that lactic acid is comrnonoly present in some di- 

 seases, and this production is essentially associated with 

 fatigue.(See works of Schmidt, Von Frey e Zuntz). 



The production of oxalic acid is associated with certain 

 cachectic conditions, and carbonic oxide may be produced 

 from oxalic acid. 



It seems more than probable that the action of afferent 

 nerves may tend further to diminish the consumption of oxy- 

 gen, and a state can be attained where the venous blood 

 seems as pure as the arterial. This is done through the des- 

 cending trophic fìbres, can these be influenced? Experiments 

 would seem to show that the activities of a tissue may cease 

 for the ti me being under nerve influences, and it may be 

 proved that the action of certain nerves may lead to des- 

 truction of tissue, especially if these nerves be subject to sti- 

 mulation or irritation. As nerve influences nave either of 

 these effects so one is familiar with the tendency in orga- 

 nisms to rest after a period of activity and to yield after a 

 prolonged period of excitement unduly set up. 



The continuous subdivision that leads to the ill-ordered 

 organisms of certain protozoic groups is perhaps to be paral- 

 leled in the new growths that form so conspicuous a feature 

 in modera medicine. Ili organized embryonic cells owe per- 

 haps their origin to undue stimulus at first, and when by 

 some chance a state of unstable equilibrium is reached in 

 the protoplasmic constituents the enzymes are man:;factured 

 without stint and the cells increase with alarming rapidity. 

 The plant seed is inoperative at first, but once the enzyme 

 becomes sufficient in quality and quantity the heat of spring 

 oanses an indefinite increase of the cells. Professor Langley 

 sees reasons for the view that trophic nerves, as advocated 

 by Waller and Brodie, are not sufficient to account for 





