APPLICATIONS OF THE GRAPHIC METHOD. 171 
a tissue may not be lost in the higher; hence the resort to ex- 
periments which have long been thought to settle the matter: 
1. The curare experithent may be thus performed: Lift up 
the sciatic nerve of a frog, and ligature the whole limb (ex- 
clusive of the nerve) so that no blood may reach the muscles; 
then inject curare, which paralyzes nerves but not muscles, 
into the general circulation through the posterior lymph-sac. 
On stimulating the sciatic nerve the muscles of the leg beneath 
the ligature contract, while no contraction of the muscles of 
the opposite leg follows from stimulation of its sciatic nerve. 
In the latter case the curare has reached the nerve terminals 
through the blood; in the former, these were left uninfluenced 
by the poison. If, now, the muscle itself be directly stimulated 
in the latter case, contraction follows, from which it is con- 
cluded that curare has destroyed the functional capacity of the 
nerve (terminals), but not of the muscle. 
2. Stimulation of those parts of muscles in which no nervous 
terminations have been found, as the lower part of the sartorius 
muscle in the frog, is followed by contraction. 
3. Certain substances (as ammonia), when applied directly 
to the muscle, cause contraction, but are not capable of pro- 
ducing this effect when applied to the nerve. 
From these and various other facts it may be concluded that 
muscle possesses independent irritability. 
APPLICATIONS OF THE GRAPHIC METHOD TO THE STUDY 
OF MUSCLE PHYSIOLOGY. 
It is impossible to study the physiology of muscle to the 
best advantage without the employment of the graphic method; 
and, on the other hand, no tissue is so well adapted for investi- 
gation by the isolated method—i. e., apart from the animal to 
which it actually belongs—as muscle; hence the convenience of 
introducing at an early period our study of the physiology of 
contractile tissue and illustrations of the graphic method, the 
general principles of which have already been considered. 
The descriptions in the text will be brief, and the student is 
recommended to examine the figures and accompanying ex- 
planations with some care. 
Chronographs, Revolving Cylinders, ete.—Fig. 164 represents one 
of the earliest forms of apparatus for the measurement of brief 
intervals of time, consisting of a simple mechanism for pro- 
