CLASS IV. 1. 1. OF ASSOCIATION. 365 



sensorial powers, as with pain or pleasure, which are in this case 

 not the proximate cause of motion, but which, by becoming a 

 link of catenation, excite the sensorial power of association into 

 action; as the pain at the neck of the gall-bladder occasioned 

 by a gall-stone is transferred to the other end of that canal, and 

 becomes a link of catenation between the action of the two ex- 

 tremities of it. 4. The influence of ethereal fluids, as of heat 

 and gravitation. To which last perhaps might be added mois- 

 ture and oxygen gas as constituting necessary parts of the system, 

 rather than stimuli to excite it into action. 



H. The Origin of Associations. 



Some trains or circles of associate motions must have been 

 formed before our nativity, as those of the heart, arteries, and 

 capillaries; others have been associated, as occasion required 

 them, as the muscles of the diaphragm and abdomen in vomit- 

 ing; and others by perpetual habit, as those of the stomach with 

 the heart and arteries directly, as in weak pulse during sickness; 

 with the capillaries directly, as in the flushed skin after dinner; 

 and lastly, with the cellular absorbents reversely, as in the in- 

 creased absorption in anasarca during sickness; and with the ir- 

 ritative motions of the organs of sense reversely, as in vertigo, 

 or sea-sickness. Some of these associations shall be here shortly 

 described to facilitate the investigation of others. 



First, other congeries of glands occupy but a particular part 

 of the system, or constitute a particular organ, as the liver, or 

 kidneys; but those glands, which secrete the mucus, and per- 

 spirable matter, which are called capillaries, are of very great 

 extent; they receive the blood from the arteries, separate from 

 it the mucus, which lines every cell, and covers every cavity of 

 the body; and the perspirable matter, which softens and lubri* 

 cates the whole surface of the skin, and the more extensive sur- 

 face of the air vessels, which compose the lungs. These are 

 supplied with blood by the perpetual action of the heart and ar- 

 teries, and have therefore their motions associated with the for- 

 mer, and with each other, by sympathy, which is sometimes di- 

 rect, and sometimes reverse. 



One branch of this association, the capillaries of the skin, is 

 very irritable by the increased quantities of cold and heat; ano- 

 ther branch, that of the lungs, has not the perception of cold 

 and heat, but is liable by direct sympathy to act in concert with 

 the former, as in going into the cold bath. And it is probable 

 foe capillaries of the internal membranes are likewise directly 



