RHYTHMICAL CONTRACTIONS IN MUSCLE 535 



able to beat rhythmically in the serum of blood containing 

 Ca. Greene has recently shown that when CaCl 2 is added 

 to a physiological NaCl solution in a concentration equal to 

 that in which it exists in the serum, the pulsations of the 

 ventricle cease, while rhythmical irritability continues. That 

 is the same behavior, therefore, as is the case with the 

 rhythmical contractions of the gastrocnemius, and we may 

 therefore assume that for the heart-beat the same circum- 

 stances come into consideration as for the rhythmical con- 

 tractions of skeletal muscle; with the exception, of course, 

 'of the conditions for the conduction of the stimulus which 

 we have discussed under paragraph 2. The role of the 

 hydroxyl ions for the heart activity might also be the same 

 as that we have found to be the case for the rhythmical con- 

 tractions of skeletal muscle. 1 The further we carry the 

 analysis of the two processes, the more complete, I believe, 

 we shall find their identity, with the exception, of course, of 

 the conditions of conductivity of the stimulus. I find only 

 two contradictory facts. One is originated by Howell that 

 NaCl is only of osmotic significance in the activity of the 

 heart. So far as the ventricle is concerned, this statement 

 of Howell's is contradicted by the observations of Aubert. 

 The second assertion comes from Howell's pupil, Greene. 2 

 Greene has observed very correctly that CaCl 2 in the same 

 concentration as it exists in the serum prevents the rhythmi- 

 cal contractions of the ventricle. Then, however, he adds 

 the following assertion, that "when the amount of CaCl 2 in 

 the serum is slightly increased, regular contraction begins." 



i 1 have recently tried to determine how many free hydroxyl ions the blood con- 

 . tains in the unit volume. I find that it cannot possibly be more, and is probably 

 less, than those present in the same volume of a one-thousandth normal NaOH solu- 

 tion. Until now we have always made the alkalinity determination of the blood by 

 titration. For the specific alkalinity of the blood, however, only the active alkalin- 

 ity that is, the concentration of the free hydroxyl ions in the blood comes into 

 consideration. It has since been found by Friedenthal, Fraenckel, Farkas, and 

 Hoeber that blood has a neutral reaction. [1904] 



2 GREENE, American Journal of Physiology, Vol. II (1898). 



