246 Animal Intelligence 
alterations of the animal’s ‘ natural’ or ‘normal’ structure— 
as by cuts, bruises, blows, and the like, — and deprivations 
of or interference with its ‘natural’ or ‘normal’ activities, — 
as by capture, starvation, solitude, or indigestion, — are in- 
tolerable. But interference with the structure and func- 
tions by which the species is perpetuated is not a sufficient 
criterion for discomfort. Nature’s adaptations are too 
crude. 
Upon examination it appears that the pernicious states of 
affairs which an animal welcomes are not pernicious at the 
time, to the neurones. We learn many bad habits, such as 
morphinism, because there is incomplete adaptation of all 
the interests of the body-state to the temporary interest of 
its ruling class, the neurones. So also the unsatisfying 
goods are not goods to the neurones at the time. We neglect 
many benefits because the neurones choose their immediate 
advantage. The neurones must be tricked into permitting 
the animal to take exercise when freezing or quinine when 
in a fever, or to free the stomach from certain poisons. 
Satisfaction and discomfort, welcoming and avoiding, thus 
seem to be related to the maintenance and hindrance of the 
life processes of the neurones rather than of the animal as a 
whole, and to temporary rather than permanent mainte- 
nance and hindrance. 
The chief life processes of a neurone concerned in learning 
are absorption of food, excretion of waste, reception and 
conduction of the nerve impulse, and modifiability or change 
of connections. Of these only the latter demands comment. 
The connections formed between situation and response 
are represented by connections between neurones and neu- 
rones, whereby the disturbance or neural current arising in 
the former is conducted to the latter across their synapses. 
The strength or weakness of a connection means the greater 
