208 PHYSIOLOGY. 



increased action of the heart and arteries (CLXXXI.), and 

 that most of the other secretions are increased only by stimu- 

 lants applied to their organs. These stimulants may be either 

 such as are immediately applied externally or internally to the 

 excretory, or perhaps to the secretory vessels, or they may be 

 such as are applied to the sensorium, or to distant parts of the 

 nervous system, which by the laws of the animal economy have 

 a connexion with the organs of secretion. These stimulants, at 

 the same time that they act in either of these ways on the se- 

 cretory organs, for the most part have no sensible effect on the 

 general state of the circulation of the blood. 



CCLXXXIII. With respect to the influence of the con- 

 dition of the common mass of blood upon the several secretions, 

 we presume that the state of the quantity of the fluids in gen- 

 eral will affect the quantity of every secretion ; but the effects 

 of the quantity of the whole mass are very remarkable only 

 with respect to the secretions of perspiration, urine, and milk. 



The qualities of the common mass may also be presumed to 

 affect the several secretions ; but the effect of these qualities 

 appears most remarkable in the same secretions of perspiration, 

 urine, and milk ; and even in these the effect seems to depend 

 upon the proportion of water more than upon that of any other 

 matter in the common mass. With respect to the other secre- 

 tions, we cannot perceive that any of them are increased by a 

 particular matter present in the mass of blood, except it be such 

 a matter as stimulates the secretory organ. 



CCLXXXIV. The several secretions are frequently ob- 

 served to affect each other mutually, so that the increase of one 

 diminishes another, and vice versa. This seems to depend 

 either upon a change of determination in the course of the blood 

 (CLXXVIIL), or upon a change in the state of the fluidity of 

 the common mass, or perhaps upon a connexion established be- 

 tween the different organs of secretion as parts of the nervous 

 system ; and, except it be in the case of perspiration and urine, 

 we cannot perceive that the effect of the state of one secretion 

 upon that of another, depends upon an increase or diminution 

 of any particular matter in the mass of blood. 



CCLXXXV. After mentioning these generalities with re- 

 spect to secretion, we should, perhaps, proceed in the next place 



