PHYSIOLOGICAL ACTION OF ORGANIC CHEMICAL COMPOUNDS. 168 



pulmonaiy vessels, so that there is immediate resistauco to the passage of 

 blood through them. Three well-observed facts support this opinion : — 1st, 

 the fact already dwelt upon, that in cases of rapid death the lungs are emptied 

 of blood ; 2nd, that the arrest of the systemic circulation commences on the 

 venous side of the circulation, and is attended with filling of the veins ; 

 3rd, that immediately after the death of the animal, if the chest be opened 

 and the heart exposed, the right side of the heart, relieved of pressure, will 

 immediately recommence to contract vigorously, showing that it is not itself 

 paralyzed, but is restrained from action by mechanical resistance to its column 

 of blood. 



If the theory of the action of narcotic vapours thus propounded be cor- 

 rect, we ought to draw from it this practical lesson, that in introducing 

 new narcotic vapours into practice, the utmost care should be taken to select 

 those only that are negative in respect to their action upon the vessels of the 

 minute circulation. A gas or vapour that asphyxiates but docs not irritate 

 may be safer than a gas or vapour that does not asphyxiate and does 

 irritate ; for the former, when it kills, kUls by a secondary process that is 

 preceded by a series of symptoms foreteUing the danger ; while the latter, 

 Avhen it kills, kUls often by instantly shutting off the column of blood that 

 is making its way to the air, and by so oppressing the heart that every 

 attempt at action, under the condition produced, increases the injury. 



Ojt CoirroxsiVE Movements ditring Narcoiism. 

 I have endeavoured to show in the last section that under narcotism from 

 certain narcotic vapours, the vapours of the chlorine series specially, there 

 are two orders of cessation of the circulation, — the one primary, beginning in 

 the lesser or pulmonary, the other secondary, beginning in the larger or 

 systemic circulation. Coineidently with these changes I have, I think, 

 observed, when there has been time for the development of the phenomena, 

 two distinct series of convulsive movements or paroxysms of convulsion. 

 I have noticed the same fact in drowning, and also in fatal sudden haemor- 

 rhage, as in the process of killing animals, such as sheep. The phenomena 

 may at any time be observed at the abattoir ; they arc in fact perhaps best 

 seen in cases of rapid fatal haemorrhage ; and I am led to the conclusion that 

 they have one common interpretation as to cause, the hsemorrhagic convul- 

 sions being the purest tj'pe of all. The convulsive actions, primary and 

 secondary, are due, as it seems to me, to disturbance of the balance of supply 

 of blood to the -nervous and muscular centres. As a mechanism, the mass of 

 nervous matter is the centre of reserved force, while the mass of muscle is 

 the moving centre, the two centres being connected by an intervening nervous 

 cord, and each supplied with the same blood. The two centres are held in 

 counterpoise, as it were, by the blood. If there be, then, any disturbance of 

 support in either centre, it wiU be indicated in change of function in the 

 moving centre, in change of motion. 



When we draw blood from the systemic circuit, or when through the 

 lesser circulation we arrest the free current of blood through the systemic 

 circuit, we destroy the balance previously existing between the musciilar and 

 nervous centres. If we could so exhaust the body that both centres should 

 be exhausted together evenly, it is possible that there would be no change of 

 motion in the moving centre ; and, indeed, in some cases of disease we see the 

 gradual and equal exhaustion without manifestation of the convulsive pheno- 

 mena. But in cases of extreme and sudden break of balance, it follows neces- 

 sarily that the balance shall be broken unevenly. It is in the muscular system 



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