No. 2.] CHANGES IN NERVE CELLS. 121 



It may be noted that both Mr. W.'s and Mr. L.'s measure- 

 ments make the difference greater than my own. Staining and 

 structure of protoplasm not well defined ; due probably to the 

 fact that the frog died toward end of experiment. At its close 

 the muscles were beginning to pass into rigor mortis. 



It was thought desirable at this stage to ascertain whether 

 the results above detailed for frogs hold good for a mammal. 

 So far, experiments have shown that the most marked results 

 are to be obtained by keeping the animal in the most normal 

 condition. Functional activity of the nerve cells of a mammal 

 can certainly not be studied many seconds after the circulation 

 is stopped ; whereas an animal is active for hours at a time, and 

 the experiments, if success is to be attained, must be continued 

 for a similar time. I think I am justified in distrusting the 

 influence of curare even upon the central portion of the reflex 

 arc. Narcotics and anaesthetics, although they do not stop the 

 cardiac and respiratory movements, if given in proper amount, 

 produce most profound changes in the activity of nerve centres. 

 So far as known, they may or they may not cause correspond- 

 ingly marked histological changes in the nerve cells. However 

 this may be, it was determined to run no risk of complicating 

 matters by their use, and accordingly a method of producing 

 insensibility without the use of drugs was resorted to. 



The cat was chosen for farther experiment. The method ^ of 

 procedure is briefly as follows : The cat is laid on a holder and 

 gently brought under the influence of ether. When fully anaes- 

 thetized, the skull is trephined at about the parietal eminence, 

 and a slit made through the dura, care being taken to dodge 

 any blood-vessels which may be in the neighborhood. The 

 trephine used was about 5 mm. in diameter. With kittens it is 

 possible to lift out a small piece of bone with the point of a 

 knife-blade with generally less loss of blood than is occasioned 

 by trephining. Now, holding the head with the left hand, the 

 thumb upon the vertex, the tip of the first finger upon the 

 angle of the right jaw, the tip of the third finger upon that of 

 the left jaw, introduce, through the opening in the skull, the 

 blunt end of a 3 mm. glass rod, and aim it directly at the angle 



1 This method was obtained from a paper entitled " On the renal circulation dur- 

 ing fever" (Walter Mendelson, Amer. Jour. Med. 5a., Phila., 1883), where the 

 method is credited to Ludwig. 



