CLASS IV. 2. 1. 10. OF ASSOCIATION, 405 



retarding his pulse. This curious circumstance cannot arise 

 from the general effect of exercise, or fatigue, as in those cases 

 the pulse becomes weaker and quicker; it must therefore be as- 

 cribed to a degree of vertigo, which attends all those modes of 

 motion, which we are not perpetually accustomed to. 



Dr. Currie has further observed, that u in cases of great de- 

 bility the voluntary muscular exertion requisite in a swing pro- 

 duces weariness, that is, increases debility; and that in such in- 

 stances he had frequently noticed, that the diminution of the fre- 

 quency of the pulse did not take place, but the contrary. 5 ' These 

 circumstances may thus be accounted for. 



The links of association, which are affected in the vertigo oc- 

 casioned by unusual motion, are the irritative motions of the 

 sense of vision, those of the stomach, and those of the heart and 

 arteries. When the irritative ideas of vision are exerted with 

 greater energy at the beginning of vertigo, a degree of sensation 

 is excited, which is of the pleasurable kind, as above mentioned; 

 whence the associated trains of irritative motions of the stomach, 

 and heart, and arteries, act at first with greater energy, both by 

 direct sympathy, and by the additional sensorial power of sensa- 

 tion, whence the pulse of a consumptive patient becomes stronger 

 and consequently slower. 



But if this vertigo becomes much greater in degree or dura- 

 lion, the first link of this train of associated irritative motions 

 expends too much of the sensorial power, which was usually em- 

 ployed on the whole train; and the motions of the stomach be- 

 come in consequence exerted with less energy. This appears, 

 because in this degree of vertigo sickness supervenes, as in sea~ 

 sickness, which has been shewn to be owing to less energetic ac- 

 tion of the stomach. And the motions of the heart and arteries 

 (hen become weaker, and in consequence more frequent, by their 

 direct sympathy with the lessened actions of the stomach. See 

 Supplement, I. 12. and Class II. 1. 6. 7. The general weak- 

 ness from fatigue is owing to a similar cause, that is, to the too 

 great expenditure of sensorial power in the increased actions of 

 one part of the system, and the consequent deficiency of it in 

 other parts, or in the whole. 



The abatement of the heat of the skin in hectic fever by 

 swinging, is not only owing to the increased ventilation of cool 

 air, but to the reverse sympathy of the motions of the cutaneous 

 capillaries with those of the heart and arteries; which occurs in 

 all fevers with arterial debility, and a hot or dry skin. Hence 

 during moderate swinging the action of the heart and arteries 

 becomes stronger and slower, and the action of the capillaries, 

 which was before too great, as appeared by the heat of tbe skin. 



