250 MORRIS M. WELLS. 



that when he put a large number of fishes (up to a maximum) 

 into a given volume of distilled water, they lived longer than 

 one or two fishes placed in the same volume of water. He at- 

 tributes this to the excretion by the fishes of inorganic salts, 

 and does not take into consideration the carbon dioxide factor 

 which would have increased the acidity of the water to many 

 times that of the almost neutral distilled water. Again, in 

 speaking of the salts which are best for preserving life in distilled 

 water, Ringer states that the calcium salts are better than those 

 of sodium and potassium, that CaSo 4 is better than CaCb 

 and that the phosphate of lime (Ca3PO 4 ) 2 is much superior to 

 all the other salts. This latter salt, he states, is decidedly acid, 

 and he says ('86) "it is interesting to observe that though the 

 circulating fluid with phosphate of lime gives a slight acid reaction 

 to delicate blue litmus paper it will sustain contractility of 

 muscle for hours." Thus a small hydrogen ion concentration 

 seems to be beneficial, if not essential, to the continued life and 

 activity of the organisms and tissues in question. 



The question of the existence of a carbon dioxide optimum 

 for animals has received considerable investigation with varying 

 results. Ringer in 1893 investigated the influence of carbonic 

 acid upon the frog's heart and concluded that free CO^ in saline 

 solution arrests cardiac contractility. He does not state what 

 concentrations of CO2 were used, but since he speaks of passing 

 carbonic acid through the solution "for some time," his solutions 

 were probably very acid. In a few experiments he neutralized 

 the slightly acid distilled water which was used to make up the 

 saline solutions, with NaOH, and noted that in this neutral 

 solution, the contractions of the heart very soon became ab- 

 normal. Jerusalem and Starling ('10) review the literature 

 regarding the importance of carbon dioxide for the ordinary 

 functions of the body, and report a series of experiments to 

 determine its influence upon the beat of the heart of the frog, 

 tortoise and mammal (cat). They conclude that the CO 2 tension 

 in the blood must be maintained at a certain height, if the pump- 

 ing action of the heart is to be normally carried out. In their 

 review of the literature they point out that their conclusions 

 are in accord with those of Miescher, Haldane, Mosso, Hender- 



