New Gulvank Discoveries. 53 



ir\ adult frogs during; the coupling season, the flexors alone 

 contract, and in particular the flexor muscles of that thigh 

 to which the silver or negative metal is applied, contract at 

 the instant when the metals come into contact, while those 

 of the thigh to which the zinc or positive metal is applied, 

 contract at the instant of their separation. — Opposite cflects 

 are obscrvahle infrogs the excitability of which is on the point 

 of being extinguished (Ritler's fifth degree). In this case the 

 extensors only contract, and the flexors remain absolutely 

 motionless. At the moment of contact of the metals the 

 muscles on the zinc side alone are thrown into action, and 

 at the moment of separation those on the silver side. 



M. Ritter distinguishes three degrees of mean excitability. 

 At the second degree (the first of the three mean degrees), 

 when the metals are brought into contact, a strong excite- 

 ment of the flexors takes place on the silver side, and a 

 weak excitement of the extensors on the zinc side; and 

 w'hen the metals arc separated a stron<! excitement of the 

 flexors is seen on the zinc side, and a weak excitement of 

 the extensors on ttie silver side. 



At the fourth decree of excital)ility the contrarv takes 

 place. At the third or middle degree the excitability ap- 

 pears to be equally distributed, the contractions on each 

 side appearing ecjual, and at the moment of contact the 

 flexors contract on the silver side, the extensors on the zinc 

 side ; while at the moment of seyxiration the extensors con- 

 tract on the silver side, and the flexors on the zinc side. 



All these phaeuomeua were cxliibited to me by M. Hitter, 

 and the different contractions were veiv easv to be distin- 

 guished. I have not had time to repeat these experiments, 

 and I fear, easy as they aj)peared tf) be, thcv will require an 

 experienced hand to produce such distinct effects as I wit- 

 nessed. P2ven with him, none of the experiments which I 

 saw succeeded the first time. 



M. Hitter, after showino; me his experiments on the dif- 

 ferent contractibility of various muscles, made me observe, 

 that the pic ce of gold tralvaniscd bv conimunication exerts 

 at once the action of two metals, or of one constituent part 

 of the pile; and that the half which in the circle was next 

 the negative pole became positive, and the half towards the 

 positive |)ole became negative. 



Having discovered u way to galvanise metals, as iron is 

 rendered maajnetic, aud b.avinjr found that the tialvauised 

 metals always exiiibir two poles, as the niagnciic needle 

 docs, JNl. Ritter suspended a galvanised gold needle on a 

 pivot. He perceived, to liis surprise, llial these lui dles^ 



D 3 had 



