40 



Scientific Proceedings (36). 



In the frog the femoral blood vessels in one leg were ligated 

 and the two gastrocnemius muscles connected with levers. Sta- 

 tionary electrodes were placed beneath the sciatic nerves and by a 

 suitable arrangement of keys an induced current could be led into 

 either nerve at will. After establishing the control response in 

 both muscles from 1.0 to 1.5 c.c. of the salt in saturated solution 

 was introduced into the dorsal lymph sac. The nerves were stimu- 

 lated at intervals and the results recorded. 1 



Results. — 1. Injection of 1.0 to 1.5 c.c. saturated solution of 

 magnesium sulphate into the dorsal lymph sac of a 20 to 30 gram 

 unpithed frog is soon followed by a loss of muscular response to 

 nerve stimulation while direct stimulation of the muscle remains 

 as effective as before the injection. 



2. The limb whose blood vessels were previously ligated 

 showed no such loss of response to nerve stimulation. 



It may be remarked that it is known that other salts, e. g., 

 sodium chloride also have a curare-like action. 



B. In Relation to Sensory Stimulation. 



After ligating the femoral blood vessels to one leg in frogs, 

 the response to sensory stimulation, e. g., thermal, electrical, chem- 

 ical (acid) and mechanical stimulation of the skin of the fore and 

 hind limbs was recorded by contraction of the gastrocnemius mus- 

 cles. Magnesium salts, 1.0 to 1.5 c.c. saturated solution, were 

 then injected into the dorsal lymph sac. After a time no response 

 in the unligated leg could be elicited by stimulating as before, but 

 the muscles in the ligated limb responded strongly. At this 

 stage the muscles in the unligated leg responded strongly to direct 

 stimulation, but not at all to nerve stimulation. In such an ex- 

 periment at this stage the animal is still breathing well and there 

 are no indications of insensibility. 



A rabbit was poisoned with magnesium salt solution admin- 

 istered subcutaneously. After a time one sciatic nerve was ex- 

 posed and stimulated with an induced current. Upon stimulation 

 of the sciatic nerve, reflex contraction of the muscles of the trunk 

 occurred while only slight or no response of the muscles supplied 

 by this nerve was observed. Direct stimulation of the muscles 



1 Detailed descriptions of the apparatus and technique employed will be included 

 with the complete account of these experiments. 



