THEIR NATUEE AND EFFECTS. 69 



the muscles usually being powerfully contracted, and 

 then relaxation takes place. Sometimes they may 

 remain tense for some time, but they are commonly 

 clonic. They are very general in character, even to the 

 muscles of the orbit. Sometimes they appear to be 

 tonic, the muscles, as it were, clasping forcibly the 

 frame of the victim. 



Dr. Weir Mitchell, in investigating the action of the 

 poison of the crotalus or rattle-snake, describes what he 

 terms a " fremitus," or trembling of the muscular 

 fibrils, dependent upon the contact of the poison with 

 the muscle. The following experiment was made, in 

 order to ascertain whether the convulsions were due 

 to this direct action of the poison on the muscles or 

 not. 



Experiment XIX. 



A fowl was placed under the influence of chloroform, 

 and its right crural nerve divided ; the left crural nerve 

 was then isolated, and a ligature placed round all the 

 other structures, so as completely to obstruct the circu- 

 lation, but the nerve was left uninjured. A small 

 quantity of solution of daboia-poison was subcuta- 

 neously injected into the tissues at the back of the 

 neck. Almost directly after, convulsions occurred ; but 

 in these convulsions the muscles supplied by the right, 

 or divided nerve, took no part, remaining perfectly 

 flaccid, while the muscles of the left leg were violently 

 tetanized. Here the muscles of the right leg, which 



