The Action of Magnesium Salts. 



39 



found to be supraminimal and at times even maximal. A similar 

 result was obtained with lactic acid, which was administered to the 

 muscle in an isotonic solution of various salts. When lactic acid 

 in a strength of 1/3200, or even 1/6400, gram-molecular solution, 

 was injected into the muscle, a stimulus heretofore subminimal 

 immediately elicited contractions. Thus both carbon dioxide and 

 lactic acid in small quantity are capable of increasing the irritability 

 of protoplasm. Gotschlich found that continued subminimal stimu- 

 lation of muscle renders it acid in reaction, even though no con- 

 tractions occurred. The conclusion therefore seems to be justified 

 that summation of stimuli may be explained as due to a rise in 

 irritability, brought about by the action on the living substance of 

 small quantities of certain products of metabolism, especially carbon 

 dioxide and lactic acid, the same substances which, in larger 

 quantity, are important factors in fatigue. 



24 (434) 



The action of magnesium salts : A. In relation to motor nerve 

 impulses ; B. In relation to sensory stimulation. 



By A. H. RYAN, F. V. GUTHRIE and C. C. GUTHRIE. 



\From the Physiological Laboratories of Washington and Pittsburgh 



Universities^ 



Since 1869 it has been generally held that magnesium salts 

 have a curare-like action (Jolyet and Cahours, Arch, de physiol., 

 1869, ii, 113 ; Binet, Rev. med. de la Suisse romande, 1892, xii, 

 523, 593 ; Wiki, Jour, de physiol. el de path, gen., 1906, viii, 794- 

 803 ; Bardier, ibid., 1907, ix, 611, and others). As this point is of 

 interest in connection with the behavior of animals after the sub- 

 cutaneous injection of magnesium salts, we have re-investigated 

 this phase of their action. 



A. In Relation to Motor Nerve Impulses. 

 Frogs have for the most part been used, though some obser- 

 vations have been made on mammals (rabbits, dogs, cats, rats, etc.). 

 As the results are in agreement for all animals so far tried, only 

 those on frogs and rabbits will be mentioned here. 



