260 G.ilvatiic Exferiiiitnts. — Vfefiil Nct'tca. 



fFrog — zinc — zinc. 

 Negative cafes. •, Frog — zinc — mufcular flefli — filver. 



L Frog — zinc — nrufcular flefli — filver— zinc. 



Mr. Humboldt fiiiifhes tliis letter by fome obfervations which he has colletled in the 

 courfe of his experiments on tUe JJhnic or ajiheiiic virtue of chemical agents; that is to fay, 

 their energy or their incfRcacy to produce irritation. Alkalis appear to be to the fenfible 

 fibres what acids are to mufcular groups. The muriatic acid augments the iritability of the 

 niufcle while it extinguiflies that of the nerves, which does not re-appear even after the acid 

 has been (iUurated with alkali. 



By continuing to bathe the nerve with an alkaline folution, an entire atony is at length pro- 

 duced by excefs of irritation ; but if a few drops of muriatic acid be let fall on the part, the 

 irritability is re-ellabli(hed. 



A thigh of a frog, irritated even to total relaxation by a warm folution of oxide of arfenic, 

 has exhibited new tonvulfions, after having been immerfed for two minutes in a folution of 

 pot-a(h. 



The flhenic virtue of the oxygenated muriatic acid is not lefs remarkable. Thighs of 

 frogs naturally flaccid, and weakened flill more by the Galvanic procefs for feven hours, 

 which afforded no fign of motion when filver ferved as a condu£lor between zinc and the 

 nerve, exhibited violent contratlions when the nerve was moiftened with oxygenated mu- 

 riatic acid. The author refers to this fubjecl the experiment which he publidied in 1793, 

 in his Flora Fribergeitfis, by which it is afcertained that ordinary muriatic acid retards the 

 germination of plants, but that oxygenated muriatic acid had caufed a plant to germinate in 

 feven hours, which required thirty-eight in pure water in order to arrive at the fame de- 

 velopment. This fact appears to him to indicate fome relation between the vegetable and 

 animal organization. 



A judgment may be formed from this extra£lof the number of important fa£ls contained 

 in this letter, and of the intereft they will excite when they (hall be colle£led, arranged, 

 and amplified, in the large work which the author is preparing. 



IV. 



Ufeful Notices refpeBitig various ObjtBs *. — Methods of clofiiig •wide-mouthed Vejfels — Preferva- 

 tion of Gunpowdei — Granulation of Shot — Precipitation of Magnefia. 



J. Methods cfclofwg wide-mouthed Veffels. 



X HE means of clofmg the apertures of large jars and other fimilar veflcls, fo as to render 

 them air-tight, has long prefented, to perfons who are engaged in philofophical purfuits, an 

 objeft of fome intereft. Thofe in particular who are in the habit of preferving animal 

 fubftances in fpirit for anatomical or phyfiological cabinets, find that, notwithftanding all the 

 care which can be taken, the evaporation of the liquor in which they are immerfed is a fub- 

 ie£l which requires conftant attention. Perhaps nothing with which we are acquainted is 



• The whole of the prcTcnt article was received frnm my anonymous correfpondcnt, J. F— : — : — :— r, whofe 

 former communications have, no doubt, engaged the attention of the reader. 



more 



