546 ANIMAL PHYSIOLOGY. 
prominent, throw some light upon these facts, and especially 
the one otherwise not easy to understand, that so much impor- 
tant work should be done by relatively so few cells. Possibly, 
however, if localization is established as fully as it may eventu- 
ally be, this also will not be so astonishing. 
Nevertheless, the doctrine that so small a region of the 
medulla as is the vaso-motor center, for example, should con- 
trol so many different vascular tracts, ought not to be finally 
accepted without close examination. It is so easy to speak of a 
“center” for any function and to locate it in the medulla; but 
it is not unlikely that the physiology of the future will greatly 
modify our present teaching in this regard. As in many other 
cases, the explanations seem to be too simple and.too artificial. 
The law of habit has, in- connection with our psychic life 
and that of other mammals, some of its most striking develop- 
ments. This has long been recognized, though that the same 
law is of universal application to the functions of the body has 
as yet received but the scantiest acknowledgment. 
We shall not dwell upon the subject beyond stating that in 
our opinion the psychic life of animals can be but indifferently 
understood unless this great factor is taken into the account; 
and when it is, much that is apparently quite inexplicable be- 
comes plain. That anything that has happened once any- 
where in the vital economy is liable to repetition under a 
slighter stimulus, is a law of the utmost importance in physiol- 
ogy, psychology, and pathology. The practical importance of 
this, especially to the young animal, is of the highest kind. 
The doctrine of a “cortical projection” for the senses, or 
cortical sense-centers, has enough foundation to enable us to 
draw certain inferences relative to the direction to be given to 
the education of youth. If true, then the education of the 
senses has a thoroughly good foundation in physiology, and 
“manual training” should receive the hearty support of sci- 
entists. It follows that in developing the senses we are devel- 
oping the most important part of the brain for all higher ends, 
the cerebral cortex. 
It will now also be clear that if there are cortical motor re- 
gions, then the size of the cerebrum and the muscular develop- 
ment may stand in a closer relation than we have been wont to 
believe. That connection of the muscular sense, tactile sensi- 
bility, sight, etc., aimed at in “ manual training,” is in harmony 
with what we have frequently urged in relation to the mutual 
AanandAanan af ann nont nf tha hmain wnan anathan Rath than. 
