194 



PRACTICAL PHYSIOLOGY. 



[XXXIV. 



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

 muscle contracts ; on slimulatiiig 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- 



I '^ t 



[4.— Scheme of the Curare Experiment. 

 Battery; /. Primary, 11. Secondary 

 spiral ; N. Nerves ; F. Clamp ; NP. Non- 

 poisoned leg; P. Poisoned leg; C. Com- 

 mutator; K. Key. Tlie short-circuiting 

 key in the secondary ciixuit is omitted in 

 the diagram. 



8. Euhne*8 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. 



{b.) Excise the sartorius of a large 

 frog, and cut it transversely into 

 five pieces of nearly equal length. 

 Plade them in their original order 

 on the filter-paper, numbering them 

 I to 5. Pass a feeble tetanising 

 current through the muscle, and 

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

 3, and 4, contract, while i and 5 

 remain quiescent. On making the 

 current stronger the terminal parts 

 also contract. Why 1 Because 

 there are no nerves at the end of 

 the sartorius. and in the first instance 

 the muscular fibres are really excited 

 by stimulation of the intramuscular 

 terminations of the nerves, while in 

 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 CHAMBBR- 

 SINQLE 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 



