212 SPECIAL PHYSIOLOGY 



forward. This gives ready access to bulbus arteriosus and aortse. 

 With an aneurysm needle pass fine thread around latter, taking care 

 not to injure auricle, and ligate. 



With scalpel cut through occipito-atlantoid membrane from side 

 to side, and bend head forward. Remove posterior wall of upper 

 end of spinal canal by inserting smaller blade of strong scissors into 

 spinal canal and cutting, taking care not to injure cord. Allow a 

 drop of the concentrated solution of strychnine to fall directly upon 

 cord; or with fine hypodermic needle inserted 1.5 cm. into the arach- 

 noid space inject two drops of the solution. 



(a) What effect has ligation of the aortse on the circulation? 



(b) Would stoppage of the circulation prevent the drug from 

 reaching the peripheral terminations or trunks of the sensory nerves ? 

 Motor nerves? Muscles? 



(c) Where, then, must strychnine act to produce the observed symp- 

 toms? 



(d) Would cessation of the circulation delay the action of strychnine 

 on the cord by slowing the rate of its absorption by the latter? 



(5) After observing results in experiment (4), destroy first the 

 upper, then the lower, portion of the cord by passing a wire down 

 the spinal cord. 



(a) How does destruction of the upper part of the cord affect the 

 convulsions ? 



(b) What is the result of the destruction of the entire cord? 



(c) Do the results agree with those of previous experiments? 

 NOTE. Destruction of the upper part of the cord during the 



preparation of the animal may take place; if so, the upper limbs 

 will not take part in the convulsions. 



(6) Further Observations and Comparisons, (a) Compare the gen- 

 eral effects of strychnine and curare in the dog. 



(b) Compare results obtained in experiments consisting of ligating 

 the thigh of a frog, except the sciatic nerve, and injecting, in the one 

 case strychnine, in the other curare. 



IV. THE ACTION OF CURARE UPON THE NERVOUS SYSTEM. 



1. Materials. One dog; two frogs; normal saline solution; curare; 

 dry cells; inductorium; hand electrodes. 



2. Preparation. Prepare the following solution: sodic chloride, 

 curare, 0.2 grm. to 10 c.c., in acidulated 20 per cent, alcohol. Pith 

 frogs. Do not fasten the dog to the board, but simply restrain 

 him. Set up electric apparatus so as to obtain single induction 

 shocks. 



3. Experiments and Observations. (1) Give a hypodermic injec- 

 tion of 0.01 grm. per kg. curare to the dog. 



