546 THE PATHOLOGY OF NIGKT-SWEATING I^ PHTHISIS. 



physical exercise, we no doubt find that the skin is suffused with 

 blood, and the sweat glands are therefore richly supplied with 

 it. But in fever we not unfrequently find that the skin is even 

 more suffused with blood, as is shown by its redness, so that the 

 glands may have an abundant supply, and yet, notwithstanding 

 this, the skin, instead of being covered with sweat, is perfectly 

 dry. This shows, then, that a free supply of blood alone is 

 insufficient to induce perspiration. On the other hand, we find 

 that perspiration may occur freely when the supply of blood is 

 exceedingly scanty. In persons stricken with sudden fear, or 

 in those at the point of death, we find that the skin is pallid or 

 livid, the surface cold, indicating that the supply of blood to it 

 is very scanty, and yet at this very moment it may be bedewed 

 with heavy drops of perspiration. This fact shows that perspira- 

 tion may occur with a scanty supply of blood. The facts are 

 exactly analogous to what we find in the secretion of saliva 

 by the submaxillary gland. In tliis gland, irritation of the 

 chorda tympani nerve causes dilatation of the vessels of the 

 gland, a copious supply of blood to it and a free secretion of 

 saliva. Irritation of the sympathetic nerve also causes secre- 

 tion of saliva, but instead of the vessels being widely dilated and 

 the circulation in the gland rapid and free, the vessels are con- 

 tracted and the circulation is very slow. We find, also, that 

 there is a similarity between the secretion of saliva and the 

 secretion of sweat, not only in the nervous conditions under which 

 they may occur, but in the way in which they are aff'ected by 

 various drugs. The effect of atropine, for example, upon the 

 submaxillary gland is to paralyse the ends of the secreting 

 nerves in the glandular structure, and the consequence of this 

 is, that when the chorda tympani is irritated after the adminis- 

 tration of a dose of atropia, the vessels of the gland dilate as 

 usual, blood flows freely througli it, but, the secreting nerves 

 having been paralysed, the secreting cells take up nothing from 

 the blood, and not a drop of saliva flows from the duct. . When, 

 on the contrary', calabar bean is administered, the effect is 

 strikingly different, far its action is not to paralyse, but to 

 stimulate the secreting nerves. In consequence of this, the 

 secreting cells begin actively to take fluid from the blood and to 



