GALVANIC DISCOVERIES. }Q\ 



animal?, but alio a difference of excitement between the 

 extenfor and flexor mufcles, according as the pofitive or nega- 

 tive pole was applied to them, or as they were acled upon 

 the intrant after the metals were brought into contact or 

 feparated from each other. 



When the excitability is at its hijrheft point of energy, as in When the exci- 

 c c'J c , A ' tability of che 



very young frogs the moment after they are prepared, or in an ; ma | is 



adult frogs during the coupling feafon, the flexors alone con- greateft, the 



tract, and in particular the flexor mufcles of that thigh to bypoficWe gaU 



which the filver or negative metal is applied, contract at thevanifm; 



inftant when the metais come into contact, while thofe of the 



thigh to which the zinc or pofitive metal is applied, contract 



at the inftant of their feparation,. 



Theoppoiite effects are obfervable in frogs, the excitability when it is lowed 

 of which is on the point of being, extinguished, (Ritter's fifth *'£^ f ° r8 

 degree.) In this cafe the extenfors only contract, and the negative, 

 flexors remain abfolutely motionlefs. At the moment of 

 Contact of the metals the mufcles on the zinc fide alone are 

 thrown into action, and at the moment of feparation thofe on 

 the filver fide. 



Mr. Ritter diftinguiflies three degrees of mean excitability. When the ecci- 

 At the fecond degree (the firft of the three mean degrees,) ^eVn^he me- 

 when the metals are brought into contact, a ftrong excitement dium and either 

 of the flexors is difplayed on the filver fide, ^nd a weak ^dtln ^ 

 excitement of the extenfors on the zinc fide ; ana when the fl-xors and ex- 

 melals are feparated a ftrong; excitement of the flexors is feen tcnfors fimulta- 



; . L. " , . r i r neous but un " 



on the zinc tide, and a weak excitement or the extenlors on equal, 

 the filver fide. 



At the fourth degree of excitability the contrary takes At the medium, 

 place. At the third or middle degree the excitability appears ^^^^J 5 

 to be equally diftribuled, the contractions on each fide appear 

 equal, and at the moment of contact the flexors contract on 

 the filver fide, the extenfors on the zinc fide ; while at the 

 moment of feparation the extenfors contract on the filver tide, 

 and the flexors on the zinc fide. 



Mr. Ritter fhowed me all thefe phenomena, and it was very 

 eafy to diftinguifh the different contractions. I have not yet 

 had time to repeat thefe experiments, but I am afraid, eafy as 

 they appeared to be, they will require an experienced hand, 

 to produce fuch diftinct effects as I faw. None of the experi- The experi- 

 ments which Mr. Ritter performed before me fucceeded with m ™ y s s f ° " c ° ee)J 



him on the firft trial. 



