ACTION OF VENOUS BLOOD ON SWEAT CENTRE. 551 



centre is stimulated, the respiratory muscles are thrown into 

 increased action, and the blood being more aerated, the amount 

 of carbonic acid in it is once again reduced to the normal But 

 supposing the respiratory centre is weakened in any way so as to 

 become less sensitive to the stimulus of carbonic acid in the 

 blood than the other two centres, this will no longer be the case, 

 and then we shall find cold perspirations occur. This is the 

 condition which I believe to be present in phthisis. The con- 

 stant stimulation of the respiratory centre by the irritation in 

 the lungs, and the violent respiratory efforts which occur in 

 coughing, so exhaust the irritability of this centre, especially 

 during sleep, that it no longer responds in the normal manner 

 to the stimulus of carbonic acid in the blood. The blood may 

 thus become more and more venous, until the carbonic acid in 

 it excites the sweat centres, and possibly also the vaso-motor 

 centres, before the respiratory centre begins to respond. 



This, then, I believe to be the pathology of night- sweating in 

 phthisis. The respiratory centre becomes exhausted by the 

 reflex irritation from the lung, so that it no longer responds so 

 readily as it ought to the stimulus directly applied to it by car- 

 bonic acid in the blood circulating through the medulla and 

 through the spinal cord. In consequence of this the blood 

 becomes more or less venous, and to this venosity, and the 

 consequent imperfect tissue change, and not, as was formerly 

 supposed, to the actual loss of fluid or sweat in the sleep, are 

 the nervous and muscular exhaustion and prostration observed 

 in night-sweats to be attributed. If this pathology were 

 correct, it occurred to me that night-sweating might be pre- 

 vented by administering some remedy which would increase the 

 excitability of the respiratory centre. Now such a remedy exists 

 in strychnia, as has been shown by Eokitanski's experiment. 

 If, then, a dose of strychnia or nux vomica were administered 

 at bedtime, the excitability of the respiratory centre ought to be 

 so much stimulated that any excess of carbonic acid would 

 excite it to increased action, and thus the accumulation of car- 

 bonic acid in the blood would be prevented, and the sweat, which 

 I have supposed to be the consequence Df such accumulation, 

 M^ould be arrested. 



