550 THE PATHOLOGY OF NIGHT-SWEATING IN PHTHISIS. 



centre is situated in the medulla, and in !N"awrocki's experiments^ 

 when the influence of this part was destroyed hy section of the 

 cord, the perspiration ceased, just as respiration and vascular 

 tone are also destroyed under ordinary circumstances. It is 

 probable, however, that in Luchsinger's experiments the spinal 

 portion of the vaso-motor centres was sufficiently powerful to 

 excite perspiration, even after the separation from the medulla. 

 These centres were found by Luchsinger to be excited, and 

 perspiration produced by increased temperature of the blood, by 

 increased carbonic acid in the blood, and also by nicotine which 

 had been introduced into the circulation. Increased tempera- 

 ture, as we well know, causes sweating, usually accompanied 

 with dilatation of the vessels of the skin, as when we are 

 exposed to a hot sun or get Marm from exertion. Tobacco, 

 on the other hand, causes sweating with diminished supply of 

 blood to the skin, the countenance becoming exceedingly pale 

 at the same time that a cold sweat breaks out, as most young 

 smokers find out by sad experience. The effect of increased 

 carbonic acid in the blood is visible in the cold sweats which 

 bedew the brows of dying persons. I have watched the pro- 

 cess, and have observed that it was just as the finger-nails, the 

 lobes of the ears, and the lips began to get livid that the sweat 

 drops began to appear on the forehead. It was a consideration 

 of this fact which led me to suspect that the sweats of phthisis 

 might be due to accumulation of carbonic acid in the blood 

 stimulating tlie sweat centres. Nor would it do this only, for 

 any imperfect aeration of the blood would lead to imperfect 

 oxidation of the products of tissue waste in the body, and their 

 consequent accumulation would produce the same soreness and 

 lassitude which come on from the accumulation through over- 

 production by excessive muscular exertion. But it may be 

 said, How is it that carbonic acid comes to accumulate in the 

 blood in this way ? In a healthy person no such accumula- 

 tion takes place, because, although carbonic acid in the blood 

 acts as a stimulus to the sweat centres, the vaso-motor centres, 

 and the respiratory centres, yet the latter are more susceptible 

 than the two former, so that whenever a slight increase of the 

 amount of carbonic acid in the blood occurs, the respiratory 



