112 PHYSIOLOGY FOR THE LABORATORY. 



Repeat the same experiment, using a small piece of 

 paper wet in dilute hydrochloric acid as a stimulus. Ex- 

 plain and give the path of the nerve impulse. Destroy 

 the spinal cord v by passing a needle down the spinal 

 column and repeat the same experiments. 



By a comparison of the results obtained, infer one of 

 the normal functions of the spinal cord in the frog. 



H. The Sympathetic System. 



Material. A frog that has been in 5 per cent formalin for three 

 or four days. The same frog that was studied for the spinal nerves 

 may be used. 



Lay open the body cavity and push aside the intestines 

 and other organs. 



I. THE SITUATION OF THE SYMPATHETIC SYSTEM, AND 



ITS CONNECTION WITH THE CEREBRO-SPINAL 

 SYSTEM. 



Just back of the kidneys find a row of small nerve 

 fibres, which run transversely from the spinal nerves to 

 the . chain of pigmented, sympathetic ganglia close to the 

 dorsal surface and along beside the vertebrae. 



II. ITS STRUCTURE. 



Notice : 



a. The two rows of sympathetic ganglia. 



b. The nerves connecting the ganglia. 



c. The sympathetic trunks which arise from the ganglia 

 and connecting nerves. 



d. The distribution of its nerves to the digestive, circu- 

 latory, and excretory organs. 



