From the Rudolph Spreckles Physiological Laboratory of the University of California. 



THE EFFECT OF VARIOUS SALTS UPON THE SUR- 

 VIVAL OF THE INVERTEBRATE HEART. 



CHARLES G. ROGERS. 



With i Plate. 



The cause which underlies the rhythmic contraction of the 

 heart has been the subject of much controversy. In recent years 

 the importance of the inorganic compounds of the blood has been 

 acknowledged by most physiologists, but the role of each of these 

 different salts in originating and maintaining rhythmic contrac- 

 tions has caused much discussion. Up to the present time 

 almost all of the work done upon the physiology of the heart has 

 concerned vertebrates alone. 



It was, therefore, a pleasure to follow the kind suggestion of 

 Dr. Loeb and use the heart of an invertebrate as the subject upon 

 which to conduct a series of experiments which may furnish an 

 answer to the following questions: What is the influence of the 

 various salts, found in the blood, upon heart action ? And, is 

 this influence the same in the crab as in the heart of the verte- 

 brates ^ 



I wish to express my thanks to Dr. Loeb for suggesting the 

 problem and for many kind criticisms during the course of the 

 work. 



METHODS. 



In the study of the problem the hearts of the marine crab 

 Brachynotus nudus were employed. This crab is found very 

 abundantly along the western shore of San Francisco Bay, be- 

 neath rocks, between tide marks. The crabs may be kept in the 

 laboratory for a considerable period without serious deterioration 

 and hence prove to be an admirable form upon which to work. 



In carrying out these experiments three general methods of 

 procedure have been employed, of which two, however, were 



