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EXPERIMENTAL PHYSIOLOGY. 



(/.) Prepare another limb and adjust it in place of A, 

 ligature the nerve of B. On stimulating the nerve of B, no 

 contraction takes place either in A or B. 



4. Secondary Contraction. 



(a.) Make a nerve-muscle preparation, and place it on a 

 glass plate (B). Dissect out a long stretch of the sciatic 

 nerve of the opposite side (A). Lay 1 cm. of the isolated 

 sciatic nerve (A) on a similar length of the nerve of the 

 nerve-muscle preparation (B), (Fig. 86). 



Fig. 86. Scheme of Secondary 

 Contraction. 



Fig. 87. Scheme of Paradoxical 

 Contraction. 



(L) Stimulate A with a single induction shock, the muscle 

 of B contracts. Stimulate A with an interrupted current, 

 the muscle of B is thrown into tetanus. 



(c.) Ligature A and stimulate again, B does not contract. 

 Therefore, its contraction was not due to an escape of the 

 stimulating current. The " secondary contractions " in B 

 are due to the sudden variations of the electromotivity 

 produced in A when it is stimulated. 



5. Paradoxical Contraction. 



(a.) Arrangement. Arrange a Daniell's cell and key for 

 giving a galvanic current. 



