186 EXPERIMENTAL PHYSIOLOGY. 



with a cork, the upper end is open (Fig. 77, B). A wire 

 connected with a key (K') short-circuiting the secondary coil 

 of an induction machine, perforates the cork. Arranged above 

 is a light lever (L) provided with an after-load (al), and moving 

 on an axis, the short arm projecting over the mouth of the jar. 

 The whole arrangement is fixed to a platform (P), with an 

 adjustable stand (S) bearing the fulcrum of the lever and the 

 after-load. The cork must be renewed with each new drug used. 



(a.) Dissect out the gastrocnemius, divide the femur with 

 the gastrocnemius attached just above the attachment of the 

 latter, and the tibia below the knee-joint. Pass a fine 

 metallic hook through the knee-joint or its ligaments, and 

 attach it to the projecting hook of fine wire fixed to the 

 short arm of the lever. Fix the tendo achillis to a hook 

 connected with the wire passing through the cork in the 

 neck of the glass cylinder. 



(b.) Fill the glass cylinder which encloses the muscle 

 with normal saline. Stimulate the muscle directly with 

 break shocks, and take a tracing. 



(c.) Remove the normal saline with a pipette, and replace 

 it with a solution of the drug whose action you wish to 

 study e.g., veratria 1 in 5000, or barium chloride 1 in 1000. 

 Study the veratria tracing (Fig. 70). 



LESSON XXXVIII. 



DIFFERENTIAL ASTATIC GALVANOMETER 

 -NON-POLARISABLE ELECTRODES- 

 SHUNT DEMARCATION AND 

 ACTION CURRENTS IN 

 MUSCLE. 



ELECTRO-MOTIVE PHENOMENA OF MUSCLE 

 AND NERVE. 



1. Thomson's High Resistance Differential Astatic Galvano- 

 meter. 



