190 



A paper was read, containing " a brief account of a particular 

 function of Ihe nervoussystem," in \vhich Dr. Marshall Hali detailed a 

 series ofexperiments tending to prove the existenceof asourceof mus- 

 cular action distinct from all those hitherto noticed by physiologists : 

 viz. volition, the irritation of the motor nerves in some part of their 

 origin or course, or that of the museles themselves. The peculiarity of 

 this motion he stated to consist in its being excited " by irritation of 

 the extrenie portion of the sentient nerves, whence the impression 

 is conveyed through the corresponding portiun of brain and spinal 

 marrovv as a centre, to the extremities of the motor nerves." 



The aniraals experimented on vvere Salamanders, Frogs andTurtles. 

 In the first of these the tail, entirely separated from the body, moved 

 as in the living animal, on being excited by the point of a needle 

 passed lightly over its surface. The motion ceased on destroying 

 the spinal raarroiv wilhin the caudal vertebrcB. The head of a frog 

 having been removed, and the spine divided bet\veen the third and 

 fourth vertebrtp, an eye of the separated head was touched : it 

 was rctracted and the eyelid closed, a similar movement being ob- 

 served in the other eye. On removing the brain these phaenomena 

 ceased. On pinching the skin or the toe of one of the anterior 

 extremities, the \vhole of this portion of the animal moved. On 

 destroying the spinal marrovv this phaenomenon also ceased. Precisely 

 similar effects were observed on pinching the skin or toe of one of 

 the posterior extremities ; and on removing the lašt portion of the 

 spinal marroNv this phaenomenon ceased. The head of the turtlecon- 

 tinues to movė long after its separation from the body : on pinching 

 the eyelid it is forcibly closed ; the mouth is opened and the mem- 

 branc expanded under the lovver javv dcscends as in rcspiration. 

 On pinching any part of the skin of the body, extremities, or tail, the 

 animal movės. The posterior extremities and 'tail being separated 

 together, the former vvere immoveable ; the latter moved on the ap- 

 plication of the flame of a lighted taper to the skin. Those extremities 

 had no connexion with the spinal marrovv. All movement ceased in 

 the tail also on vvithchavving the spinal marrovv from its canal. 



" Three things," Dr. Hali observes, " are plain from these obser- 

 vations : 1. that the nerves of sensibility are impressible in portions of 

 an animal separated from the ręst; in the head, in the upper part of 

 the trunk, in the lovver part of the trunk : 2. that motions similar to 

 voiuntary motions follovv these impressions made upon the sentient 

 nerves : and 3. that the presence of the spinal marrovv is essential 

 as the centrai and cementing link betvveen the sentient and motor 

 nerves.'' 



Dr. Hali then proceeded to adduce another series of experiments 

 still more conclusive. If a frog be made to svvallovv a vvatery solution 

 of opium, it becomes affected vvith symptoms very similar to those of 

 tetanus and hydrophobia ; the body and limbs become rigidly ex- 

 tended ; bnt besides this statė of spasm, the cutaneous nerves be- 

 come extremely susceptive, and the motor nerves extremely excita- 

 tive ; a shake, a touch, a breath of air even, induces spasmodic 

 movements of the body and limbs. A frog made tetanic by opium 



