L. H. HYMAN. 



concentration of acid in terms of molar strength. Hydrochloric 

 acid decreased both oxygen consumption and carbon dioxide 

 output of the muscle markedly, the decrease varying from 15 

 per cent, in 1/200 mol. HC1 to 72 per cent, in 1/20 mol. HC1. 

 Thunberg also tested the action on gaseous exchange of the 

 frog's muscle of a large number of organic acids, including mono-, 

 di-, tri-, and oxycarboxylic acids of both the paraffin and olefin 

 series. Each acid was tested in the following concentrations: 

 i/ioo, 1/25, i/io, and 1/5 molecular strengths. In the majority 

 of the acids, both the oxygen consumption and carbon dioxide 

 production were decreased at all concentrations but not very 

 greatly so. The maximum decrease with the strongest concen- 

 trations was 15-25 per cent. In some of the acids (e.g., propionic, 

 butyric, lactic), the respiratory rate was increased in the more 

 dilute concentrations, decreased in the stronger solutions. In 

 fumaric, malic, and citric acids, the carbon dioxide output was 

 greatly increased, while the oxygen consumption was but little 

 altered. On the other hand, oxalic and malonic acids were found 

 to decrease the carbon dioxide output to a much greater extent 

 than the oxygen consumption. Succinic acid alone decreased 

 the former while increasing the latter. It must be remarked 

 that the concentrations used by Thunberg are extremely high 

 and it is difficult for me to believe that the muscle could have 

 remained uninjured in any of the solutions employed by Thun- 

 berg, even though each experiment lasted for only thirty minutes. 

 Exposure to 1/50 or 1/20 mol. HC1, for instance, concentrations 

 used by Thunberg, is, I believe, rapidly fatal to any living tissue. 

 Thunberg does not consider the possibility of injury to the muscle 

 in his experiments and makes no statements concerning the 

 condition of the muscle during or after the exposure. I do not 

 believe his experiments can be accepted as of physiological 

 significance. Gray ('24) has studied the action of acids on the 

 oxygen consumption and activity of ciliated tissues of bivalves. 

 Acetic, butyric, and hydrochloric acids were used, presumably in 

 sea-water. In the acidified water, both ciliary activity and 

 oxygen consumption were diminished and in relation to the 

 amount of acidity. Acetic acid at a pH of 4.6 to 4.2 and butyric 

 acid at 4.2 caused a very great decrease and even complete 



