XI.] GENERAL PROPERTIES OF NERVOUS TISSUE. 119 



all however tending to remove the irritating 

 substance. 



1 2. Wash off all the acid from the frog, and when it 

 has become perfectly quiet, place it in a basin of 

 water; it will sink to the bottom (unless the 

 lungs be accidentally much distended with air), 

 and no movements of any kind will be witnessed. 



Observe tJiat all ike movements produced in tJie fore- 

 going observations, although complicated, co-ordinated, 

 and purposeful in character, are partial, and only by 

 accident bring about locomotion. However stimulated, 

 the animal never springs or haps forward. 



In order that the same frog may serve for observations 

 on the lymph-hearts, B. I. 1 should be performed 

 liere. 



13. Make a small cut through the skin of the back 1 , 

 and with a fine glass tube inject one drop of a 

 1 p.c. solution of strychnia. In a few minutes 

 the slightest stimulus applied to any part of the 

 animal will produce violent tetanic spasms of the 

 whole body. A preliminary stage of increased 

 reflex action may also be observed. 



14. With a straight seeker or a piece of stout wire 

 destroy the whole of the spinal cord. Observe 

 that the spasms immediately cease. 



1 Immediately underneath the skin of the back of the frog is the 

 dorsal lymphatic sac, and any fluid placed in this rapidly makes its 

 way into the blood. 



