11 



III. MUSCLE-NERVE. 



I. What is the Influence of the Brain and the Spinal 

 Cord on Skeletal Muscle ? 



METHOD. Study, draw and describe the attitude, and note 

 the movements and the effect of touching and of turning 

 the animal on its back 



(1) in a frog with the brain and spinal cord intact. 



(2) In a frog with the brain destroyed. Holding the frog 

 by its hind legs, kill it by a stroke of its head upon the edge 

 of the table, and cut off its head behind the tympanic mem- 

 branes. 



After a few minutes, study and describe the attitude, 

 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. 



(Reflex Action, p. 27, may be done here.) 



(3) In a frog with the brain and spinal cord destroyed. Pith 

 the frog by passing a thick pin down the vertebral canal 

 so as to destroy the spinal cord (fig. 4). Note carefully 



FIG. 4. Pithing Frog. 



anything that takes place in the muscles as this is done. 

 Study and describe the frog again as to attitude, movements, 

 effect of touching and pinching. Examine the consistence of 

 the muscles. 



CONCLUSIONS. What is the influence of 

 (a) The brain, and 

 (6) The spinal cord upon the muscles ? 



