280 University of California Publications in Zoology [Vol. il 



in most cases within fifteen or twenty minutes. Upon removal 

 to clean water the leeches within two or three hours recovered 

 sufficiently to perform slow but co-ordinated movements. 



6. Magnesium Sulphate 



According to Cushny (1910), the magnesium salts have a 

 ver.y powerful action when injected into the higher animals either 

 hypodermieally or intravenously. The most characteristic effect 

 is complete anesthesia resembling that induced by the chloro- 

 form group and ending in fatal cases in paralysis of the respira- 

 tory center. 



A strength of magnesium sulphate as high as N % required 

 a rather long period to produce complete depression. In from 

 one to one and a half hours this had occurred. As can be seen 

 from the accompanying table (see table XII), there is at first 

 an increasing excitement, this being followed by a correspond- 

 ingly slow depression. To a certain extent, at least, paralysis 

 seems to take place in the muscles, a knotted twisting of the 

 body occurring. Later this was followed by relaxation, no re- 

 sponse other than a slight lateral movement of the anterior end 

 occurring even to very strong stimulation. This treatment seems 

 to have been more fatal than any of the other substances tried; 

 since out of four individuals tested only one revived to any 

 extent in twenty-four hours, and this not to a stage where co- 

 ordinated movements could take place. 



TABLE X 



Influence op Cocaine Upon the Duration op the Swimming Eesponses 

 Evoked by Repeated Contact Stimulation 



Duration in seconds of swimming response in ten specimens 

 Order of Dina mirrostoma 



of stimu-/ ^ ^ 



lation 1234567 89 10 Average 



1 18 25 138 215 190 150 185 200 6 10 113.7 



2 265 12 4 6 15 5 4 50 230 9 60 



3 7 125 2 4 5 3 6 7 10 222 38.6 



4 056321265 15 4.5 



5 .... 271001122 1.6 



6 .... 3 2 2 0.7 



7 .... 17 0.8 



8 .... 2 0.2 



9 



