HYDE: EXPERIMENTS ON THE SKATE. 33 



the same solution, seeking the weakest solution that produced 

 any change in the three functions under consideration; also, 

 which concentration proved toxic, and whether the injurious 

 dose could be modified or antagonized by a definite dose of an- 

 other salt. 



Observations were made and curves secured before, during 

 and after the injection of the salt solutions. From one to five 

 minutes after the injection a change in one or more of the 

 functions under consideration usually occurred, and this was 

 followed by a second change that lasted from five to twenty 

 minutes, before the records again assumed their normal char- 

 acter. The first effect may be the reaction of the salt upon the 

 constituents of the blood and indirectly upon muscle and nerve 

 cells ; the second is due to osmotic pressure changes. That in- 

 jections of hypertonic salt solutions in the blood of the dog in- 

 creases the osmotic pressure, which may become normal within 

 twenty minutes, was proved by Magnus.^ Moreover, those 

 salts that set free 0, CO2, H, or OH ions, in their reactions, 

 exert their influence more often through these ions, and effect 

 results that differ from those produced by salts having the 

 same cations, but do not react with the same resulting ion 

 products; e. g., NaCl is different in its effects from Na2C0:!, 

 probably because of the OH ions set free by the Na2C03 dis- 

 sociation. 



It is possible that the blood pressure, respiratory and cardiac 

 activities depend upon the number of molecules and ions in the 

 blood, and upon the dissociation tension of the salts. The pre- 

 potent anions or cations may stimulate or inhibit enzyme ac- 

 tion, and thus aid in producing the inner stimulus that affects 

 alike the force of cardiac and respiratory activity and directly 

 or indirectly the blood pressure. 



A careful study of very many experiments with the same 

 salts was made, the average results summed up, and the most 

 typical of a series of experiments put in tabular form. Thus 

 table n gives a survey of the different series of experiments and 

 is a summary of all the experiments conducted on the skate 

 with NaCl solutions. It shows that m 32, m/16, m/8, NaCl 

 solutions produce as a rule practically no change in the heart 

 or respiratory activity or blood pressure. An m% NaCl solu- 



4. Magnus, Archiv fiir Experimentelle Pathologie, 1900, vol. 44, p. 99. 



