194 



PKACTICAL PHYSIOLOGY. 



[XXXIV. 



solution of curare in two watch-glasses. On stimulating the nerve of A, its 

 muscle contracts ; on stimulating the nerve of B, its muscle does not contract, 



but the muscle contracts when it is 

 stimulated directly. In A, although 

 the poison is applied directly to the 

 nerve-trunk, the nerve is not para- 

 lysed. 



8. Kiihne's Curare Experiment. 



(a.) To the margin of a meat-plate 

 fix two copper slips, to serve as 

 attachments for the electrodes, and 

 between the copper terminals place 

 a strip of filter-paper moistened with 

 normal saline. 



(&.) Excise the sartorius of a large 

 frog, and cut it transversely into 

 five pieces of nearly equal length. 

 Place them in their original order 

 on the filter-paper, numbering them 



"/ ( ^ ""X -jj x \ i to 5. Pass a feeble tetanising 



/ romimiiiBHimii IMlflfflf Imlfifl current through the muscle, and 



( I note that the central parts, i.e., 2, 



y ^PHHIl imHHHL^^ 3' an ^ 4> contract, while I and 5 



remain quiescent. On making the 

 current stronger the terminal parts 

 also contract. Why? Because 

 FIG. i i 4 ,-Scheme_of_the Curare ^Experiment. there are no nerves at the end of 



y . the sartorius and in the first instance 



C* 



^-^ 



K 



poisoned leg; P. Poisoned leg; C. Com- the muscular fibres are really excited 

 imitator; K. Key. The short-circuiting by stimulation of the intramuscular 

 key in the secondary circuit is omitted in terminations of the nerves whi i e in 

 the diagram. ., , , ' ,, , , 



the case of the end parts of the 



divided muscle the muscle was stimulated directly. 



(c.) If a curarised sartorius be experimented on in the same way all the 

 parts contract at once, because all the motor nerves in the muscle are para- 

 lysed. 



LESSON XXXIV. 



THE GRAPHIC METHOD-MOIST CHAMBER- 

 SINGLE CONTRACTION. 



1. Recording Apparatus. Use a revolving brass cylinder or 

 other moving surface covered with smoked glazed paper. The 

 velocity of the moving surface is usually determined by recording 

 simultaneously the vibrations of a tuning-fork of known rate of 

 vibration, or an electro-magnetic time-marker, or by a vibrating 

 reed (p. 211). It does not matter particularly what form of 



