P. K. Gilman 229 
Tadpoles kept in the fatiguing apparatus for the longer periods of 
time became so accustomed to the stimulation and the strange surround- 
ings. that they required a longer teasing with the needle to bring to a 
condition where they were unable to respond to stimul. Stimulation 
for as short a period as three hours produced changes as marked, to all 
appearances, as those due to the longer periods of stimulation. 
B. GAsSTROCNEMIUS OF FroG.—The sciatic nerve of one side was care- 
fully dissected out and severed through as small an aperture as possible. 
! a _ This was done well above the knee 
Sess ae Rati feats to exclude any effect of air contact 
Wiiyeee ess Bea accom fpaases 
oe St erie Sire : upon the muscle. ‘The nerve was 
¢ gpa zeyetats Sre Poni 2 f : 
Hise oe - stimulated with an induction cur- 
Wee 2-5 
aa 5 
aa rent too weak to produce complete 
i . . 
tetanus. The stimulation was con- 
Set eats = tinued until no further response 
immers. Carm, Zeiss. was obtained, then the tissue in 
both legs was killed by the injection of picro-acetic acid through the 
abdominal aorta, thus insuring identical conditions in this respect for 
both muscles. After fixation the skin about the muscles was ruptured for 
the first time and two muscles, stimulated and control, carried together 
through the same jars of reagents as described above. 
Where the normal nuclei 
’ j ; : et See ers pret 
are regular in outline and eweiehs ee ; a f nner 
show a marked granular ap- we eengege 
pearance (Fig. 3) those of 
the fatigued muscle are 
shrunken, irregular in out- —-Fia.4. Stimulated muscle. Gastrocnemius of 
line (Fig. 4) and more ho- from js oil immers. Carm. Zeiss. 
mogeneous. The granules or the nuclei are finer and stain less intensely 
than those of the resting muscle nuclei. 
In the figures typical sections are represented, many of the sections 
showing even more marked differences, nuclei in some cases being 
shrunken to half their original size. 
Experiments were performed attempting to demonstrate the effect of 
fatigue on heart muscle nuclei. Kittens were used and both vagi sev- 
ered in the animal experimented upon to allow an increased heart rate. 
A control animal of approximately the same size was used in each 
case. Although a greatly increased heart rate was obtained and the 
animals kept alive for periods up to ten hours, no histological evidences 
16 
