ON INDUCED CONTRACTION. 
647 
duced contraction are always obtained stronger and more durably on the muscles 
of the thigh and leg, than on the other parts of the frog. 
Exp. 2. Induced contraction is very evident at the moment when the muscle itself, 
on which is laid the nerve of the galvanoscopic frog, is divided. This experiment 
is perfectly analogous to that which is made by cutting, in different directions, a very 
small piece of the organ of the torpedo, upon which a nerve of the galvanoscopic frog 
has been placed. 
Exp. 3. Induced contraction is produced in the same manner, and with equal in- 
tensity, whatever may be the direction in which the nerve of the galvanoscopic frog 
is extended, in respect to the muscular fibres. 
Exp. 4. If we interpose between the nerve of the galvanoscopic frog and the sur- 
face of the thigh of the entire frog several layers of wet paper, we cease to obtain 
induced contraction : if there is only a layer or two of very thin paper, induced con- 
traction continues to be produced. 
Exp. 5. We dispose a prepared frog, as in Plate L. fig. 1 ; « c and h d are two glass 
tubes covered with varnish, upon which the frog is fixed by means of Indian rubber 
rings, e and f-, g and h are two bits of linen, or of thick paper moistened with salt 
water. If we touch separately the point g or the point h with the nerve of the gal- 
vanoscopic frog, there is no sign of induced contraction ; but if the nerve of the galva- 
noscopic frog be disposed as in fig. 1, so that the nerve touches at the same time the 
points g and h, we have immediate contraction in the galvanoscopic frog, exciting 
contractions in the muscles of the entire frog. This takes place in whatever manner 
the contractions are provoked, whether by wounding or cutting the spinal marrow, 
or in passing an electric current from a small pair of zinc and platina along the lum- 
bar nerves. 
Exp. 6. If, while making the preceding experiment, a communication be established 
between the two legs of the frog, by placing a wetted cotton wick over the points t s 
or jp and q, or over all the intervening points, the contractions of the galvanoscopic 
frog cease instantly, although the members of the entire frog are in contraction : we 
have only to remove the cotton wick and the phenomenon reappears. These alter- 
natives are constant, and are always reproduced in the same manner. 
Exp. 7. The results of the preceding experiments are obtained whether the legs of 
the entire frog are brought into contact or whether they are kept separate. We see 
from this the advantage of the arrangement adopted in these experiments in order to 
avoid placing the frog on a plane, which would soon become moistened and serve as 
a conductor. 
Exp. 8. By means of a solution of the extract of nux vomica, I produce a state of 
nervous superexcitation in the frogs. While in this condition these animals are sub- 
ject at intervals to violent contractions, which may also be excited by the slightest 
contact. I place a frog in this condition on the apparatus, fig. 1 . The galvanoscopic 
frog rarely gives signs of contraction, while the entire frog contracts violently. One 
