322 OP THE PRIMARY TISSUES OF THE HUMAN BODY. 



sions on the Nervous system, in diminishing, where it does not altogether de- 

 stroy, Muscular irritability, is well seen in the operation of severe injuries affect- 

 ing vital organs, or extending over a large part of the surface, in depressing the 

 Heart's action. This is a well-known result of severe burns, especially in chil- 

 dren, whose nervous system is more susceptible of such impressions than that 

 of the adult; also of the rupture of the alimentary canal, of the bladder or 

 uterus; and of the shattering of one of the extremities, by violence affecting a 

 large part of their substance. In all these cases, the sufferer is in the same 

 condition with one who has received a severe blow on the head that does not 

 quite stun him ; the shock immediately diminishes the muscular contractility of 

 the whole system; and its influence on the heart, which of course manifests 

 itself most conspicuously, produces a degree of depression, which is frequently 

 never recovered from, and which at any rate renders necessary the employment 

 of stimulants, for the purpose of counteracting this very dangerous effect. 1 

 Excessive mental Emotion, of a kind not in itself depressing, may occasion the 

 sudden cessation of the heart's action, and a general loss of muscular irritability; 

 and it is well known that muscular power is greatly diminished by emotions, 

 which produce no other direct action. 



322. There is no evidence that Muscular irritability can be increased by any 

 cause operating through the Nervous system. It is quite true that, under the 

 agency of alcohol, nitrous oxide, or some of the other substances that rank as 

 stimulants, individuals can perform actions requiring a degree of strength, which 

 they cannot exert under ordinary circumstances. But it does not hence follow 

 that the irritability is increased; since the energy of the movement is attributa- 

 ble solely to the increase of the nervous power by which it is excited, and to the 

 unusual number of fibres called into simultaneous contraction. We have numer- 

 ous examples of this kind, in cases in which the stimulus is purely mental ; a 

 state of general emotional excitement producing a temporary augmentation of 

 the nerve-force transmitted to the muscular system, as is seen in violent fits of 

 passion, and still more in Mania; or an extraordinary amount of nerve-force 

 being determined to particular groups of muscles by the concentration of the 

 attention upon them, in peculiar states of Abstraction, without any emotional 

 excitement whatever (see CHAP. xiv. SECT. 7). It is well known that stimu- 

 lating agents, which temporarily increase Muscular power, primarily excite the 

 Nervous system ; as is shown by the increased mental activity which results 

 from the moderate use of alcohol, nitrous oxide, opium, &c. ; and it does not 

 seem necessary, therefore, to go further, in search of an explanation of their 

 effect on muscular action. 



323. There can be no question that the condition most essential to the main- 

 tenance of Muscular contractility, is an adequate supply of arterial blood. It 

 is well known that, when a ligature is applied to a large arterial trunk in the 

 Human subject, there is not only a deficiency of sensibility in the surface, but 

 also a partial or complete suspension of muscular power, until the collateral 

 circulation is established. The same result has been constantly attained, in 

 experiments upon the lower Animals; the contractility of the muscle being 

 impaired or altogether extinguished, when the flow of blood into it was arrested ; 



1 The large quantity of stimulus which can be borne even by children, suffering under 

 severe burns, is very extraordinary. There can be no doubt that many lives have been 

 saved by the judicious administration of them, to an amount, which would a priori have 

 been judged in itself fatal ; but that many more have been sacrificed to neglect, even on 

 the part of those whose duty it is to watch the indications with the closest attention. The 

 Author's observations lead him to believe that Hospital Nurses very commonly make up 

 their minds that children, who have met with severe burns, must die ; and that, unless 

 closely watched, they neglect the means of which Science and Experience alike dictate 

 the free employment. 



