1885.] Comparative Physiology and Psychology. II 
“ Cogito ergo sum,” Huxley regards as “non sequitur.” I would 
merely postulate both ends of the sentence as being for physio- 
logical study, unassailable: “Sum et cogito,” and let the meta- 
physicians wrangle over the rest. The Amceba’s functions are 
simple but nevertheless the same as our own. Forthwith we 
must assign it a desire for food, which desire is the chemical 
affinity of atoms, then the Amceba hungers. This, Professor E. 
D. Cope? assigns as “the primitive desire and a form of pain. 
This was followed by gratification, a pleasure, the memory of 
which constituted a motive for a more evidently designed act, viz., 
pursuit.” 
Dividing primitive desires arising from (or with, if you wish) 
the atomic affinities into those which subserve and those which 
oppose assimilative processes, we have the origin of pain and 
pleasure, under which two heads all conscious workings may be 
classed. 
Pain increases with the quantity of atoms unsatisfied. As long 
as there are protoplasmic molecules with affinities, the number of 
them wanting food increases the desire (attraction directly as the 
mass). Of course as soon as destructive starvation breaks down 
the molecules the desire ceases. 
This is evident in the final loss of desire for food in extreme 
deprivation in man. 
All unsatisfied desire is painful, as : 
Hunger in the absence of food. 
Desire to move about while disabled from so doing. 
Desire to excrete when prevented by any cause. 
In the act of satisfying desires pleasure is apparent : 
Hunger appeased. : 
Movement unconstrained. 
Emunctories unobstructed and excretion active. 
All pains and pleasures are relative and intense in proportion 
to the precedence of one or the other extreme. 
The pangs of parturition are obstructive excretory, and what 
obstetrician has not noticed the happiness of accomplishment by 
the mother. 
A pleasure is often wholly due to the preéxistence of pain, and 
bearing upon the evolution of the reproductive excretory cellular 
into a desire which in its influence upon animal life is second 
1 Origin of the Will, Penn Monthly for June, 1877, p- 446. 
