94: NERVOUS SYSTEM. 



properties and the differences in the manner of its disappear- 

 ance. The woorara-poison, a very curious agent prepared 

 by the South- American Indians, has the remarkable prop- 

 erty of paralyzing .the motor nerves, leaving the nerves of 

 sensation intact. This fact has been demonstrated by Ber- 

 nard and others by very curious and ingenious experiments. 

 The poison, like those of animal origin, acts most vigorously 

 xfter introduction under the skin or absorption from wounds, 

 and produces no toxic effects when taken into the stomach, 

 except when introduced in large quantity in fasting animals. 

 Under the influence of this agent, an animal dies with com- 

 plete paralysis of the motor system, presenting, among other 

 phenomena, arrest of respiration. Most of the varieties of 

 the poison affect only the motor nerves, and do not influence 

 the action of the heart ; and in animals brought completely 

 under its influence, artificial respiration will enable the heart 

 to continue its action, and, in some instances, if this be per- 

 sisted in, recovery will take place. 



The fact that the woorara-poison affects the motor nerves 

 only has been experimentally illustrated by Bernard, tak- 

 ing advantage of the reflex functions of the spinal cord to 

 show the persistence of the irritability of the sensory nerves. 

 The most striking of these experiments is the following : A 

 frog is prepared by exposing the nerves in the lumbar re- 

 gion, and then isolating the posterior extremities by apply- 

 ing a strong ligature, including the aorta and all the parts 

 except the nerves ; so that, practically, the only communica- 

 tion between the posterior extremities and the body is by 

 the nerves. It is evident, therefore, that if the poison be 

 introduced under the skin of the body, acting, as it does, 

 through the blood, it will affect all parts except the poste- 

 rior extremities ; for the poison acts from the periphery to 

 the centres, and must circulate in the parts to which the 

 motor nerves are distributed. If the posterior extremities 

 be now irritated, the impression is conveyed to the spinal 

 cord through the sensory filaments of the lumbar nerves, 



