l6o WITHROW MORSE. 



]\Iercier had injected the grains, appeared in the muscle masses 

 undergoing atrophy. 



Granting that this explanation is adequate, we may seek the 

 more immediate factor involved. The first suggestion may be 

 that oxygen inhibits the activity of the autolyzing enzymes and 

 that when the blood supply is interfered with, the inhibiting 

 action of oxygen is thrown off, permitting autolysis. The experi- 

 ments of the writer (22) speak decidedly against this theory of 

 inhibition of autolysis by oxygen. 1 



The known relation between reaction of medium and autolysis, 

 of which we have spoken earlier in the present paper is sufficient 

 to afford an adequate explanation of what takes place at the 

 inception of autolysis. Partial interruption of the blood supply 

 everywhere results in an accumulation of carbon dioxid. The 

 "buffer" value of the blood in alkalinity is soon neutralized and 

 an actual acidity of the blood results (Ph<7). Perhaps, like- 

 wise, as in starvation, acids other than carbonic acid enter the 

 blood stream, such as those of incomplete oxidation the so- 

 called acids of acidosis, ketonic acids, beta-hydroxybutyric acid, 

 aceto-acetic acid and the keton ace ton. Even in the total exclu- 

 sion of respiratory oxygen, intramolecular oxidation occurs, 

 giving rise to carbon dioxid and to the acids of acidosis. This 

 the writer takes to be the modus operandi of atrophy in the larval 

 frog. 



With regard to oxygen, the following experiment of the writer 

 bears : 



Experiment. Several tall glass cylinders, 45 cm. high and 5 

 cm. in diameter were filled with water and into each was intro- 

 duced a single larva which gave no evidence of metamorphosis. 

 The larvae were fed algae, .but owing to the darkened space in 

 which the experiment was conducted, photosynthesis, giving rise 

 to oxygen, did not occur. The jars were left for several weeks, 

 during w r hich time the larvae grew, but none of them exhibited 

 any tendency towards metamorphosis. Controls in finger- 

 bowls with oxygenated water metamorphosed. 



1 The recent papers by Burge in the American Journal of Physiology contain the 

 assumption of oxygen inhibition, but there is no experimental data to substantiate 

 the theory. 



