490 
David 11. Dollev 
that if such Stimuli work at all the effect produced is tlie same as that 
from natural Stimuli. 
In the second niethod, the important facts are that the Stimuli, 
while imusual, can hardly be considered abnormal, and more essential, 
they must be received by the normal receptor apparatus in its normal 
way. The apparatus is iUustrated in Text Figure 1. It consists of a 
water-wheel, made of tin, three feet in diameter, of which the picture 
is sufficient description. The important point about it is that the rim 
is so inclosed on both sides as to form a contiiiuous water-tight gutter, 
in which the crayfish was placed along with sufficient water. AMien the 
wheel turns, the anhnal clings to the bottom untü he is carried out of 
the water, back to which he continuously attempts to crawl. If the 
wheel run too fast, or he momentarüy cease his efforts, he is canied to 
a point too steep for adherence and then slips back into the water. At 
the beginning there is a distinct straining attempt on the part of claws, 
legs and flipper to hold more securely. This is further proved by the 
fact that as the animal becomes more and more fatigued, his movements 
become more and more passive. That the procedure is enthely effi- 
caceous is shown by the more rapid fatality and the more marked reaction 
of certain cell types at least from thhty six hours in the wheel (Experi- 
ment 23) than from two weeks of electrical Stimulation (Experiment 19). 
Technic of fixation and staining. 
A Solution of fornialin-sublimate consisting of 95 parts of saturated 
mercuric Chloride and 5 parts of the 40% solution of formaldehyde was 
used for the routine fixation. On account of the difficulty in remo\ing 
the Chain of ganglia in the fresh state, it was found more convenient 
to expose them in situ by removing the superimposed dorsal sheU and 
the thoracic and abdominal tissues. Thereby the ventral portion of the 
Shell Avas left as a support, and when tied to a cardboard the enthe chain 
was kept straight, while it also afforded a more rapid procedure. After 
a fixation of four to six hours, the tissue was run through the graded 
alcohols. It was customary to finish the removal of the ganglia in 
50% alcohol, and this and the succeeding Solutions of 703o and 80°o 
were iodized to remove the excess of Sublimate. From xylol imbedding 
was done in paraffin. Longitudinal sections Avere cut in serial of five 
niicra thickness and fastened to slides by the Avater niethod. 
Erythrosm-toluidin blue AA'as employed as the routine stain. After 
removing the paraffin in the usual Avay, the sections were stained about 
