280 NERVOUS FORCE. LECT. XIV. XV. 



two ; but I have never seen it in four. These, then, are 

 induced contractions of the first, second, and third order. 



Before deducing from the facts which I .have now made 

 known, the conclusions which may be drawn from them, 

 there remains for me to relate to you the numerous experi- 

 ments which I have made, with the view of discovering 

 what influence is exercised upon induced contraction, by 

 bodies interposed between the contracting muscle and the 

 nerve of the galvanoscopic frog. 



In my first experiments upon induced contractions, I had 

 remarked that, by spreading a leaf of gold (such as is used 

 for gilding) upon the inducting muscles, and afterwards 

 placing upon one of the muscles, covered over with this 

 small layer of gold, the nerve of the galvanoscopic frog, 

 the induced contraction was no longer produced. In order 

 to render this experiment successful, the muscle must be 

 completely covered with gold ; and it does not succeed, 

 after one or two contractions, by which the metallic leaf has 

 become torn. 



I have also observed, that a leaf of glazed paper, placed 

 between the muscle and the nerve, likewise prevented this 

 same contraction. On the contrary, filtering paper, mois- 

 tened with water, or with the serous liquid which moistens 

 the surface of the muscles, when placed between this lat- 

 ter and the nerve of the galvanoscopic frog, offers no 

 obstacle to the production of these induced contractions. 



Our knowledge respecting the influence of interposed 

 bodies on this phenomenon, was at first confined to the 

 observation of these three facts. I have recently endea- 

 voured to extend and vary the experiments. The mode of 

 experimenting which I adopted, consists in preparing a 

 frog, after the manner of Galvani, and placing it on turpen- 

 tine ; at the same time an assistant prepared other galvano- 

 scopic frogs, the nerves of which I placed upon the muscles 



