Class III. 2. 1. 3. OF VOLITION. 333 



3. 2. 2. which originate from excefs of fenforial power, or from 

 efforts to relieve difagreeable fenfation, and are afterwards con- 

 tinued by habit. 



3. Tremor fetrilis. Tremor of old age confifts of a perpetual 

 trembling of the hands, or of the head, or of other mufcles, 

 when they are exerted ; and is erroneoufly called paralytic ; and 

 feems owing to the fmall quantity of animal power refiding in 

 the mufcular fibres. Thefe tremors only exift when the affect- 

 ed mufcles are excited into action, as in lifting a glafs to the 

 mouth, or in writing, or in keeping the body upright ; and ceafe 

 again, when no voluntary exertion is attempted, as in lying 

 down. Hence thefe tremors evidently originate from the too 

 quick exhaultion of the leiTened quantity of the fpirit of anima- 

 tion. So many people tremble from fear or anger, when too 

 great a part of the fenforial power is exerted on the organs of 

 fenfe, fo as to deprive the mufcles, which fupport the body 

 erect, of their due quantity. 



4. Brachiorum paralyfis. A numbnefs of the arms is a fre- 

 quent fymptom in hydrops thoracis, as explained in Clafs I. 2. 

 3. 14. and in Sect. XXIX. 5.2.*, it alfo accompanies the aflhma 

 dolorificum, Clafs III. 1. 1. 11. and is owing probably to the 

 fame caufe in both. In the colica faturnina a paralyfis affects 

 the wrifts, as appears on the patient extending his arm horizon- 

 tally with the palm downwards, and is often attended with a tu- 

 mor on the carpal or metacarpal bones. See Clafs IV. 2. 2. 10. 

 and I. 2. 4. 8. 



Mr. M , a miner and well-finker, about three years ago, 



loft the power of contracting both his thumbs ; the balls or muf- 

 cles of the thumbs are much emaciated, and remain paralytic. 

 He afcribes his difeafe to immerfmg his hands too long in cold 

 water in the execution of his bufmefs. He fays his hands had 

 frequently been much benumbed before, fo that he could not 

 without difficulty clench them •, but that they recovered their 

 motion, as foon as they began to glow, after he had dried and 

 covered them. 



In this cafe there exifted two injurious circumftances of dif- 

 ferent kinds ; one the violent and continued action of the muf- 

 cles, which deftroys by exhaufting the fenforial power ; and the 

 other, the application of cold, which deftroys by defect of ftim- 

 ulus. The cold feems to have contributed to the paralyfis by 

 its long application, as well as the continued exertion ; but as 

 during the torpor occafioned by the expofure to cold, if the de- 

 gree of it be not fo great as to extinguifh life, the fenforial pow- 

 er becomes accumulated; there isreafon to believe, that the ex- 

 pofmg a paralytic limb to the cold for a certain time, as by cov- 

 ering 



