286 OF MUSCULAR CONTRACTILITY. 



Nervous System, the agency of which is one of the stimuli that can call it 

 into operation. It may be desirable briefly to recapitulate the facts by which 

 this doqtrine is supported. 1 . The existence in Vegetables of irritable tissues, 

 which are excited to contraction by stimuli directly applied to themselves, and 

 can be in no way dependent upon, or influenced by, a Nervous system. 2. The 

 existence in Animals of a form of Muscular tissue, which is especially con- 

 nected with the maintenance of the Organic functions, and which is much 

 more readily excited to action by direct stimulation than it is by nervous 

 agency. 3. The fact that, by the agency of these, the organic functions may 

 go on (as long as their other requisite conditions are supplied) after the removal 

 of the nervous centres, and when none were ever present ; rendering it next 

 to certain, that their ordinary operations are not dependent upon any stimuli 

 received through the nerves, but upon those directly applied to themselves. 

 4. The persistence of irritability in muscles, for some time after the nerves 

 have ceased to be able to convey to them the effects of stimuli ; this is con- 

 stantly seen in regard to the Sympathetic system of nerves, and the muscles 

 of Organic life upon which they operate; and it may also be shown to occur 

 with respect to the Cerebro-Spinal system, and the muscles of Animal life, by 

 the agency of narcotics. 5. The persistence of irritability in the muscles, 

 after their complete isolation from the nervous centres, so long as their nutri- 

 tion is unimpaired; and the effects of frequent exercise, in preventing the 

 impairment of the nutrition and the loss of irritability. 6. The recovery of 

 the irritability of muscles, when isolated from the nervous centres, after it has 

 been exhausted by repeated stimulation ; this also depends upon the healthy 

 performance of the nutritive actions. 7. The contraction of muscular fibre 

 under the microscope, when completely isolated from all other tissues. In 

 the words of Dr. Alison, then, " the only ascertained final cause of all endow- 

 ments bestowed on Nerves in relation to Muscles, in the living body, appears 

 to b.e, not to make Muscles irritable, but to subject their irritability, in different 

 ways, to the dominion of the acts and feelings of the Mind," to its volitions, 

 emotions, and instinctive determinations. 



386. There can be no doubt, however, that the Nervous System is capable 

 of exerting an influence upon the property itself ; for we find that sudden and 

 severe injuries of the Nervous Centres have power to impair, directly and 

 instantaneously, or even to destroy the Contractility of the whole Muscular 

 System ; so that death immediately results, and no irritability subsequently 

 remains. It is in this manner, that the sudden destruction of the Brain and 

 Spinal Cord, especially of the latter, occasions the immediate cessation of the 

 heart's action ; though they may be gradually removed, without any consider- 

 able effect upon it. Severe concussion has the same effect ; hence the Syn- 

 cope which immediately displays itself. It is sometimes an important question 

 in Forensic Medicine, whether an individual, who has died from the effects of 

 a blow upon the head, could have moved from the place where the blow was 

 inflicted. If there be found, as is frequently the case, no sensible disorgan- 

 ization of the Brain, the death must be attributed to the concussion, and must 

 have been in that case immediate. If, on the other hand, effusion of blood 

 has taken place within the cranium to any considerable extent, it is probable 

 that the first effects of the blow were in some degree recovered from, and that 

 the circulation was re-established. It is not essential, however, that the im- 

 pression should be primarily made upon the Cerebro-Spinal system. The 

 well-known fact of sudden death not unfrequently resulting from a blow on 

 the stomach, especially after a full meal, without any perceptible lesion of the 

 viscera, clearly indicates that an impression upon the widely-spread coeliac 

 plexus of Sympathetic nerves (which will be much more extensively commu- 

 nicated to them, when the stomach is full, than when it is empty), may cause 



