The Morphology of Fimctional Actmtj' in the Ganglion Cells etc. 499 
Finally, the changes will be fouiid to differ only in degree, not in 
kind. They vary in extent, in tlieir collectivc approximation to a resting 
condition on the one hand or to a state of fatigue on the other, but they 
are the same in natiire. ExperimentaUy, the only change produced 
was that more cells approach exhaustion. In every animal, normal or 
stimulated, every cell could be apportioned to a definite place in the 
same constant cycle. This cycle then can only be the varied expression 
of States of normal cellular acti\äty even if the activity be carried to 
unusual limits. 
As the pah’ of cells just mentioned would appear to have a consider- 
able value as a general Index of the fimctional state of the animal and 
as technicaUy at least they are ideal for comparative purposes, certain 
technical points will be inserted here which would save much labor and 
trouble to any future investigator, It is unnecessary to serial the entire 
ganglion. These two cells are located in the median ventral portion of 
the cephalic end of the supra-oesophageal ganglion, being irabedded 
in the supporting tissue between the lobes. The point of origin of the 
longitudinal commissure, which is dorsal, serves to identify the dorsal 
and ventral surfaces at the moment of imbedding. Unless imbedded 
very obhquely anteroposteriorly, they will be found to lie superficiaUy, 
within the first one fourth of the block, a matter of moment when the 
total number of sections may comprise 300 in the smaUer animals. 
The analysis of cell types and the presumptive Separation into motor 
and sensory groups. 
In the beginning of the study, the necessity of distinguishing be- 
tweeii the different types of ceUs became obvious. The preliminary 
measurements showed that otherwise there was no correlation. It will 
be clearer to state the essential bases of this distinction first though it 
is to be remembered that the minor particulars are affected considerably 
by the functional state of the ceU. The presence (Figs. 1—12) or absence 
(Figs. 13 — 22) of the intracellular axone, running throughout the length 
of the ceU and usuaUy partly around the nucleus, is the main point 
of drfferentiation into groups. In the more numerous group this is en- 
tirely lacking. The cells with the intracellular axone are in general 
obviously considerably larger. These two groups differ also in ap- 
pearance in other minor particulars, with or without activity, so that 
there is no question of their being separate entities. Essentially, the 
larger cells possess a greater density although their chromatic granula- 
