558 ANIMAL PHYSIOLOGY. 
the importance of sensations derived both from the skin and 
the muscles for co-ordination of muscular movements, 
In locomotor ataxy, in which the power of muscular co- 
ordination is lost to a large extent, the lesions are in the pos- 
terior columns of the spinal cord, or the posterior roots of the 
nerves, or both, and these are the parts involved in the trans- 
mission of afferent impulses, 
Whether the muscular sense also implies a central “ neural ” 
sense, or consciousness of the changes of central origin, associ- 
ated with the execution of a movement as distinct from the 
impressions derived from the muscles, is a matter of dispute. 
But the student will be already prepared for our answer to this 
question. The evidence of experiment seems to point to a dis- 
tinct source of information in the muscles. We would take 
along with this the additional data of sense afforded by the skin, 
the “sense of effort” and other factors, as stored past experi- 
ence, which must be very variable for the individual, as any 
one may observe by watching the muscular efforts of others 
and himself. 
Comparative——The more closely the higher vertebrates are 
observed, the more convinced does one become that those sen- 
sory judgments, based upon the information derived from the 
skin and muscles, which they are constantly called upon to form 
are in extent, variety, and perfection scarcely if at all surpassed 
by those of man. Of course, a sensory judgment in man, with 
his excessive cerebral development, may by associations in his 
experience be worked up into elaborate judgments impossible 
to the brutes, but we now refer to the judgments of sense in 
themselves. 
The lips, the ears, the vibrissee or stiff hairs, especially 
about the lips, the nose, in some cases the paws, all afford deli- 
cate and extensive sensory data. 
It is a remarkable fact that the most intelligent of the 
groups of animals have these sensory surfaces well developed, 
as witness the elephant with his wonderful trunk, the hand 
of the monkey, and the paws and vibrisse of the cat and dog 
tribe. 
On the other hand, the groups with hoofs are notably inferior 
in the mental scale. When we pass to the lower forms of in- 
vertebrates the appreciation of vibrations of the air or water 
in which they live, of its temperature, of its pressure, must be 
considerable to enable them to adapt themselves to a suitable 
anwinanmant 
