MUSCULAR IRRITABILITY. 821 



fact of some importance in relation to the disputed question of the con- 

 nection of muscular irritability with the nervous system, that when, by the 

 application of narcotic substances to the nerves, their vital properties are 

 destroyed, the irritability of the muscle may remain for some time longer, 

 showing that the latter must be independent of the former. The effects 

 produced by the Woorara and Upas Antiar poisons in this respect are ex- 

 ceedingly curious, and have been carefully studied by Bernard 1 and others. 

 Woorara, Couia, and, as Drs. drum Brown and Fraser 2 have shown, the 

 Sulphates and Iodides of Methyl-Strychnium, Methyl-Brucium, Methyl- 

 Thebaiura, Methyl-Codeium, and Methyl-Morphium, all act directly upon 

 the motor nerves, whilst Cyanide of Potassium and the poison of the Upas 

 Antiar abolish the irritability of the muscular tissue itself. The evidence 

 given by Bernard in proof of this last statement is very satisfactory, for he 

 has shown that the cause of death after the administration of a sufficient 

 dose of Woorara is the cessation of the respiratory movements owing to 

 paralysis of the motor nerves ; for not only has it been proved by v. Bezold 

 that by this agent the rapidity of the conduction of stimuli through the 

 motor nerves is greatly reduced and ultimately abolished, but it is certain 

 that perfect recovery may take place if artificial respiration be maintained 

 for a sufficient length of time to enable the poison to be eliminated from the 

 system or decomposed within it ; whilst in foetuses, and during the earlier 

 stages of existence of fishes and other animals that are not directly depend- 

 ent upon muscular movements for the aeration of their blood, this being 

 accomplished by the umbilical vesicle, little or no injurious effect is experi- 

 enced, the animals continuing to swim about in a watery solution of the 

 poison without apparent inconvenience. That the sensory nerves are not 

 affected seems to be proved by the experiments of Kolliker and Funke, who 

 observed that reflex actions could readily be excited in parts kept free from 

 the ciivulatiou of poisoned blood by the ligature of their vessels, on pricking 

 or pinching the skin of parts poisoned by the admission of blood containing 

 Woorara. The influence of the poison seems to be first felt by the periph- 

 eral extremities of the motor nerves, and its paralyzing effect gradually 

 extends ceutripetally through the trunks. An additional argument may be 

 mentioned in favor of the essential independency of muscular irritability, in 

 the circumstance that, although spontaneous movements occur in the muscles 

 of embryos, the muscles cannot, in the earlier periods of foetal life, be incited 

 to contract by stimuli directly applied to their nerves. Dr. Harless 3 again 

 found that when the nervous system had been rendered, by the inhalation of 

 ether, utterly incapable of conveying a galvanic stimulus applied either to 

 the nervous centres or to the nerve-trunks, the same stimulus applied directly 

 to the muscles would immediately throw them into powerful contraction. 

 Various other experimenters have shown that when the nerves supplying 

 the muscles of a limb are divided and the animals are allowed to live, excit- 

 ants applied to the nerves beyond the point of division fail to produce mus- 

 cular contraction long before they cease to do so when applied to the muscles 

 themselves. Hence it is obvious that the activity of the Nervous system is 

 not essential to the manifestation of the characteristic endowment of the 

 Muscular. 



671. The contractions of the Heart present some differences from those of 



1 See his Lecture in Med. Times and Gnzntte, 1860, vol. ii ; also A. v. Bezold in 

 Monatsbericht der Berlin. Akad., 1859 ; and Martin-Magron and Buisson in Journal 

 de la Physiolof-ie, I860. 



2 Transact, of the Roy. Soc of Eclinb., 1808. A paper of great value on the con- 

 nection between chemical constitution and physiological action. 



3 Muller's Archiv, 1847, Bd. ii. 



