Effects of direct Application of Magnesium Salts. 41 



with a current of the same strength brought a good response. 

 At this time the animal was breathing well and there were none 

 of the symptoms of asphyxia which appeared later. 



Results. — 1. The behavior of an animal in response to sensory 

 stimulation is notably altered after the subcutaneous injection of 

 magnesium salts in large amounts. Motor response may even 

 entirely disappear but a disappearance of sensitiveness is not con- 

 comitant with motor paralysis. But if previous to the adminis- 

 tration of the salt in frog, the blood vessels to a hind limb be 

 ligated, the muscles of such a limb show good response to stimu- 

 lation of the skin of the fore limbs. 



2. A rabbit poisoned with magnesium sulphate shows a loss 

 of muscular response to indirect stimulation, while at this time the 

 muscular response to direct stimulation is good. At this stage 

 the reflex mechanism is still capable of functioning as shown by 

 the contraction of trunk muscles on stimulating the central end 

 of the sciatic nerve. The more peripheral muscles seem first to 

 be paralyzed. The muscles of respiration appear to be the last to 

 become paralyzed. 



2 5 (435) 



The effects of direct application of magnesium salts : A. To 

 motor and sensory nerves ; B. To cardio-inhibitory 



nerves. 



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



[From the Physiological Laboratories of Washington and Pittsburgh 



Universities.'] 



A. The sciatic nerves in both legs of frogs were exposed and 

 three pairs of stationary electrodes placed beneath each. The 

 wiring was such that an induced current could be switched to any 

 of the six pairs of electrodes at will. After recording the control, 

 direct and reflex response of the gastrocnemius muscles, the solu- 

 tion to be tested was applied to the nerve trunk at the site of one 

 of the middle pairs of electrodes. Stimulation of the nerves was 

 continued and the result recorded. After a time the solution on 

 the nerve (or on both nerves, when two substances were being 

 tested at the same time) was removed and return of function 



