266 JOURNAL OF COMPARATIVE NEUROLOGY. 
The muscle-nerve-cord preparation was made as in the other 
members of this series. It was found after experimenting with 
one specimen that the dissection of the cord for its whole length 
produced too great injury to it, and such extended dissection is. 
unnecessary. The cord is fairly free and easily accessible to 
the electrodes. No precaution against its breaking itself in 
pieces is necessary with the leech. Unfortunately, the dis- 
section necessary to make the preparation caused the posterior 
portion of the animal to contract so strongly that it would not 
react to further stimulus and hence could not be used to make 
records of contractions. Consequently we were unable to de- 
termine the antero-posterior rate in the cord. The head end, 
however, being free from this prolonged contraction allowed 
the determination of the postero-anterior rate. This was not 
without difficulties, for the almost incessant motion of the an- 
terior part of the animal, thus continually displacing the lever 
attached to it, makes it necessary to watch very closely to catch 
the moment of rest of the animal, coinciding with proper ad- 
justment of apparatus. Still, when all was right, the stimulus 
gave prompt and decisive reaction. These conditions made it 
obviously impossible to take the records at equal intervals. 
It was found necessary to make use of the interrupted cur- 
rent, for, while single induction shocks were efficient as a stim- 
ulus when applied at the point of the cord nearest the muscula- 
ture used, they failed to produce a definite contraction when ap- 
plied at the distal point. This was true for both directions in 
the cord. However, a single induced shock applied to a point 
in the posterior end of the cord generally produced the indefi- 
nite motion of swimming or crawling. 
At the conclusion of each experiment the worm was killed 
in 5% alcohol, the cord dissected out, and measured after tak- 
ing the precaution to straighten out the loops formed in the in- 
terganglionic portions produced by the contraction of the body 
of fhe leech 
The temperature of the room varied from 16°C, to 21°C. 
EXPERIMENT No. 2, Table II, Oct. 5, Igo1. 
Distal Proximal 
No. of records 23 23 
Mean latent time 0.28 sec.| O.II sec. 
Standard deviation 0.03 sec.| 0.004 sec. 
Coefficient of variability .10 |  .036 
Length of cord: 10.25 cm. Rate: 59.4 cm. per sec. 
