310 NERVOUS SYSTEM. 



cerned in the reflex phenomena is restricted; and, after 

 section of the cord itself, the most powerful and easily-ex 

 cited movements are produced when the division has been 

 made low down in the lumbar region. He has also shown 

 that simple puncture of the cord produces an exaggeration 

 of the reflex excitability, as well as hyperaesthesia. 1 



In experiments upon animals, the reflex phenomena are 

 greatly exaggerated in intensity in the tetanic condition pro- 

 duced by poisoning by opium or strychnine. Take, for 

 example, a frog decapitated and poisoned with strychnine. 

 No reflex movements occur unless an impression be made 

 upon the sensory nerves; but the faintest irritation, such as 

 a breath of air or a slight jar, throws the entire muscular 

 system into a condition of violent tetanic spasm. The same 

 phenomena are observed in cases of poisoning by strychnine, 

 or of tetanus, in the human subject. This fact is important 

 in its relations to the treatment of these conditions ; for it 

 is evident that, in such cases, the exhaustion due to the vio- 

 lent spasms may be moderated by carefully avoiding all un- 

 necessary irritation of the surface. 



It was shown a number of years ago, by Longet, that the 

 inhalation of anaesthetic agents may abolish all of the ordi- 

 nary reflex phenomena. 2 "Whether this be due to an action 

 upon the cord itself or to a paralysis of the sensory nerves, 

 it is difficult to determine. Ordinarily, in animals rendered 

 insensible by anaesthetics, the reflex act of respiration con- 

 tinues ; but this may also be arrested, as has been observed 

 by all who have experimented with anaesthetics, especially 

 w T ith chloroform. A common way of determining that an 

 animal is completely under the influence of ether is by an 

 absence of the reflex act of closing the eyelids when the 

 cornea is touched. 



It now only remains to show that the phenomena of re- 

 flex action observed in experiments upon the inferior ani- 



1 VULPIAN, Systeme nerveux, Paris, 1866, pp. 441, 442. 



2 LONGET, Traite de physiologie, Paris, 1869, tome iii., p. 256. 



