SECTION II 

 NERVE AND MUSCLE 



LESSON VI 



The ways in which the outer world acts upon us through our 

 various receptor mechanisms having been studied, the problem of 

 how we react through our neuro-muscular mechanism may next be 

 investigated. The influence of the brain and of the spinal cord 

 upon the muscles and the way in which the nerves act upon them 

 may first be studied. 



This may be done by comparing the condition of a frog with the 

 brain intact with its condition after the brain has been destroyed. 

 The spinal cord is then the only part of the central nervous 

 system connected with the muscles and its influence may be deter- 

 mined by observing the condition before and after it is destroyed. 



Revise your knowledge of the anatomy of the brain, spinal cord 

 and nerves of the frog. With a microscope examine (1) a piece of 

 nerve teased in 0-75 NaCl solution ; (2) a transverse section of a 

 nerve stained with osmic acid, and (3) a transverse section of the 

 spinal cord stained by Weigert-Pal's method. 



A. THE INFLUENCE OF THE BRAIN ON THE SKELETAL 



MUSCLES 



Arrange an induction coil for stimulation with Neef's hammer 

 (see Appendix, p. 81). 



METHOD. Study, draw and describe the attitude of the frog 

 supplied, and note the movements and the effect of touching and 

 of turning the animal on its back 



(1) With the brain and spinal cord intact. 



(2) After the brain has been destroyed. Hold the frog by the hind 

 legs in the fold of a towel and kill it by hitting the edge of the table 

 a sharp blow with its head. Then cut off the head behind the 

 tympanic membranes. After a few minutes, study and describe 

 the attitude, the movements, and the effect of touching and pinching. 

 Feel the condition of the muscles as to consistence, and place the 

 animal on its back noting any difference in its behaviour. 



What is the influence of the brain upon the muscles and upon the 

 power of balancing ? 



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