TRANSACTIONS OF SECTION D. 501 
The object of this paper is to show that both depend on variation and 
selection acting on different kinds of units. 
The conditions—viz., struggle for existence, reproduction of organisms, and 
the destruction of unfit varieties—which accompany natural selection are also 
present during the adaptive response by somatic cells. 
The making of use-acquirements by somatic cells coincides with functional 
activity in these cells. Indirect adaptation through germinal variation coincides 
with cell division. Both depend on variation and selection among individual cells 
or among cell parts, Only those cells undergo cell division which are undif- 
ferentiated—e.g., germ-cells—or which undergo undifferentiation before division. 
The adult nerve-cell in the human subject undergoes neither undifferentia- 
tion nor cell division, but has a great capacity for intra-cellular molecular re- 
arrangement and reconstruction when exposed to altered stimuli. 
Indirect adaptation depends on the inter-cellular variations which accom- 
pany cell division. Direct adaptation depends on the intra-cellular variations 
which accompany functional activity in somatic cells. 
EXAMPLES OF USE-ACQUIREMENTS. 
Muscular Hypertrophy.—Differs from the neuro-psychic response in mode of 
origin. It is the result of cell division in muscle-cells and not of variation and 
selection of the component parts of individual muscle-cells. It is a use-acquire- 
ment on the part of the individual, but not on the part of the individual 
muscle-cell. 
The Neuro-Psychic Response.—Is a true use-acquirement. It is not accomni- 
panied by destruction or regeneration of individual nerve-cells, but is associated 
with a process of reconstruction and rearrangement of molecular composition in 
nerve-cells. The effect of an altered stimulus-is to initiate variation in the 
molecular architecture of the nerve-cell, and to favour the selection and the per- 
petuation of one out of several modes of intra-cellular metabolism in the nerve- 
cell. The consideration of neuro-psychical adaptation as a whole also favours 
this explanation of the origin of use-acquirements. The acquirement by use and 
experience of new modes of neuro-psychic response depends on the selection of 
one out of several possible modes of neural activity. 
The Acquired Immunity Reaction.—This is a use-acquirement as made by the 
individual, but it is also the result of variation and selection of body cells 
exposed to disease organisms. It depends partly on inter-cellular, partly on 
intra-cellular variation and selection. 
Use-acquirements made by somatic cells are not normally transmitted to off- 
spring, that is to germ cells and their descendants, but they are transmitted to 
the cell descendants of the somatic cells which make them. 
The origin of all use-acquirement in a process of innate variation among cell 
parts explains this apparent anomaly. 
21. Speech in Animals. By Professor R. J. ANpERson, M.D., M.A. 
There is an obvious relationship between the expression of wishes, emotions, 
&c., by means of words and the capacity to understand words. There are many 
who seem to believe that a dog, cat, or horse can be trained to understand the 
common meaning of many words. There are, on the other hand, many who 
believe that even the monkey, elephant, or parrot have a very limited capacity 
in this regard, and that the tone of voice, pose or gesture count for much with 
many animals. Association and the reflex accompaniments seem to count for 
much. A little dog will learn very soon to associate the presence of some friend 
with the licking of his lips. Salivation, which is commonly associated with the 
smell, sight, or thought of food in man, becomes in a dog associated with a nerve 
stimulus or sound, as the experiments of Pawlov and his pupils prove. The bell 
that calls the workman from labour to refreshment may lead a dog to ‘ whine’ 
or bark because of its association. A dog distinguishes between a lively tone 
and menacing tone; this may be the result of education. And the sense of 
smell is evidently the most powerful associated sense. We must agree that sight 
and hearing are not so keen as scent in dogs. The power and disposition to seize 
upon some salient feature by the eye or ear is easily recognisable. This ‘ quick- 
