Mr H. F. Baxter on Muscular Power. 197 
contraction of the gastrocnemius alone. The importance 
of confining the contraction solely to this muscle, as 
observed by Matteucci, the perineal nerve was divided, so 
as to avoid the contraction of the extensor muscles; this 
could be readily done, as the sciatic nerve is seen to divide 
into two large branches at the lower part of the thigh. Care, 
however, must be taken that the posterior branch be not 
divided ; to ascertain this point, the nerve was stimulated 
after the division, to see which muscles were contracted. 
Instead of keeping the frog in the horizontal position, ac- 
cording to the method pursued by Schwann, I found the 
following to be the most convenient and satisfactory mode 
of conducting the experiments :— 
The apparatus made use of was similar in principle to 
that employed and described by Matteucci in the Phil. 
Trans. for 1846, and to which I must refer. It consists of 
a glass stem fixed upon a wooden stand ; to this stem could 
be adjusted and fastened, by means of screws, several 
moveable pieces ; to the lower one the pulley was attached, 
and the scale upon the dial was divided into 80°. The cir- 
cumference of the pulley was 14 inch, consequently 1° of 
the scale corresponded to rather more than sd of an inch. 
The next piece above the pulley consisted of the portion 
fork-shaped, and through the holes at its extremities the 
silk passed, to prevent it from slipping off the pulley: 
to the upper end of the silk was tied a small hook ; to its 
lowest end the scale was attached which carried the weight. 
The two upper detached pieces were for the purpose of 
securing the frog ; on the lower one, which projected hori- 
zontally forwards, the frog was placed astride, one limb 
being attached to the pulley, the other limb was tied at the 
ankle, and fastened, by means of a string, to one of the arms 
of the lower piece which supported the dial ; by these means 
the two limbs were balanced when the weights were placed 
in the scale. To the upper detached piece, which projected 
_ horizontally outwards at right angles to the lower one, the 
fore-extremities of the animal were fastened by strings. By 
this arrangement the frog was firmly fixed without inter- 
fering with its breathing, and there was no impediment to 
the free circulation of the blood in the lower limbs. 
NEW SERIES. —VOL. XVIII. NO. 11.—ocToBER 1863. 2¢ 
