Sm-prlfiiig Effca of the Gnlvaiuc Lr!faf!on on IFoumh. 257 



" 111 a converfation," fays he, « with M. Scarpa, at Pavia, on the cffefls which Galvanifm 

 produced upon myfclf, notliing furprifed him more than the appearance of a lymphatic and 

 ferous humour on my baci;. « What can be the nature,' faid he, ' of this ftimulant, which 

 in a few inllants changes the nature of the vcfltls to fuch a degree as to caufe them to 

 prepare humours, which, the inftnnt they touch the epidermis, excite inflammation, and mark 

 their courfe by a rednefs which lafts for whole hours?"' M. Humboldt promifcd to repeat 

 the experiment; and the account he gives of the fafts conaitutes one of the moft intereft- 

 ing articles in his letter. 



For this purpofe he caufed two bliftering platters to be applied on the deltoid mufcle of 

 both flioulders. When the left blifter was opened, a liquor flowed out which left no other 

 appearance on the (kin than a flight varnifli, which difappeared by walhing. The wound 

 was afterwards left to dry up : this precaution was necefl'ary, in order that the acrid humour 

 which the Galvanic irritation would produce might not be attributed to the idiofyncrifis of 

 the veffels. This painful operation was fcarccly commenced on the wound, by the applica- 

 tion of zinc and filver, before the ferous humour was difcharged in abundance : its colour 

 became vifibly dark in a few feconds, and left on the parts of the flcin where it pafled 

 traces of a brown inflamed red. This humour having defcended towards the pit of the 

 ftomach, and ftopped there, caufed a rednefs of more than an inch in furface. The hu- 

 mour, when traced along the epidermis, left ftains, which after having been wafhed ap- 

 peared of a blueilh red. The inflamed places having been imprudently wathed with cold 

 water, increafed fo much in colour and extent, that Mr. Humboldt, as well as his phyfician 

 Dr. Schalleru, who affifted at thefe experiments, entertained fome apprehenfion for the 

 confequences. 



Mr. Humboldt has not undertaken to determine the nature of the fluid which produces 

 fuch aftonifliing efl^edts -, but he applies himfelf to circumfcrlbe the phenomena in the real 

 circumftances which produce them. He judicioufly varies the preparations, and carefully 

 notes all the refults ; being perfuaded that the caufe of Galvanifm cannot be explored with 

 fucccfs, but by obferving the proponions in which the chain of metals either irritates or has 

 no effea : and to extend ftill more this vaft field of obfervation, he employs various means 

 to raife or dimini(h the irritable capacity of the animal organs. 



What is the fenfation which the Galvanic irritation produces .' Mr. Humboldt has difcufled 

 this queftion. " No one (fays he) can fpeak more decidedly on this fubjeft than myfelf, 

 having made feveral experiments on my own perfon, the feat of which, in fome inftances, 

 was the focket of a tooth which I had caufed to be extra£led ; in others, certain wounds 

 which I made in my hand ; and in others, the excoriations produced by four bliftering 

 plafters." The following is his anfwer : 



The Galvanic irritation is always painful, and the more fo in proportion as the irritated 

 part is more ir-jured, and the time of irritation more prolonged. Tlie firft ftrokes are felt 

 but nightly ; the five or fix following are much more fcnfible, and even fcarcely to be endured, 

 until the irritated nerve becomes infenfible from continued ftimulus. The fenfation does not 

 at all refcmblc that wliich is caufed by ilie eledric commotion and the cledric bath ; it is a 

 peculiar kind of pain, which is neither (liarp, pungent, penetrating, nor by intermiffions, 

 like that which is caufed by the eledric fluid. We may diftinguidi a violent ftroke, arcgulir ' 

 prclTurc, accompanied by an unintcrmitting glow, which is incomparably more adivc when 



Vol . T.— SppXFMnPD %rtx-^ T t 



Vol. I. — Shi-tember 1797. u 



the 



