191 



was decapitated and divided just below the third vertebra. The eyes 

 continued drawn in, and no motion could be detected on irritating 

 the eye, eyelid, or skin. But both the anterior and posterior parts 

 remained tetanic as before. The limbs were moved in the same spaS' 

 modic manner by the same slight impressions. The exalted condition 

 of the function of the sentient and motor nerves continued in each 

 part. All was changed on removing the brain and the respective 

 portions of spinal marrow. The eyes were immovable, but no longer 

 retracted ; tlie muscles of the limbs were flaccid, and there was no 

 evidence of irritability in the sentient nerves. 



" These experiments," Dr. Hall continued, " appear to me to 

 establish a property or function of the nervous system, — of the sentient 

 and motor nerves, — distinct from sensation and voluntary or instinc- 

 tive motion. However doubtful this conclusion might appear in re- 

 ference to the first series of experiments upon the animal in its natural 

 state, it can scarcely admit of doubt when we compare with them the 

 phaenomena observed in the frog made tetanic by opium. In this case 

 the contraction of the muscles is plainly 7wt the result of volition ; and 

 it obeys the same laws, in regard to its continuance and extinction, 

 as the similar function or property in its natural and unexalted state. 

 Neither does it arise from the irritation of the motor nerves, or mus- 

 cular fibre 3 for it ceases on removing the spinal marrow, while the 

 property of irritability continues unimpaired after the destruction of 

 the nervous centre. I conclude, then, that there is a property of the 

 sentient and motory system of nerves which is independent of sensation 

 and volition ; — a property of the motor nerves independent of imme- 

 diate irritation: — a property which attaches itself to any part of an 

 animal, the corresponding portion of the brain and spinal marrow of 

 which is entire. This property is capable of exaltation, in the frog, 

 from the influence of opium, and doubtless of strychnine j and I may 

 add, that it is diminished or extinguished by the hydrocyanic acid. It 

 is naturally greatest in animals of lowest sensibilihj, as the cold- 

 blooded." 



With regard to the office performed by this property of the nervous 

 system in the animal oeconomy. Dr. Hall stated that it appeared espe- 

 cially to preside over all those functions which, from appearing 

 neither exclusively voluntary nor independent of the vviil, have been 

 designated mixed. That the function of respiration is of this kind he 

 considered plain from the pheenomena presented by the separated head 

 of the turtle, in which the submaxillary integuments became alter- 

 nately inflated and contracted as in ordinary respiration. The ac- 

 tions of coughing, sneezing, vomiting, &c. are of the same kind. 

 So apparently is the singular eft'ect produced by tickling. Of all the 

 parts of the human frame the larynx and the anus appear to be most 

 under the influence of this peculiar power. No part is so impatient 

 of irritation as the former; none so much in need of automatic 

 action as the latter, with the other sphincters. These very parts are 

 subject moreover to peculiar morbid affections of this function : in 

 regard to the larynx it is observed in some affections of dangerous 

 tendency referred to spasm : in the spliincters it is seen in those sin- 



