754 The Relations of Mind and Matter. [August, 
THE RELATIONS OF MIND AND MATTER. 
BY CHARLES MORRIS. 
(Continued from p. 691, Fuly number.) 
IIL. DEVELOPMENT OF THE NERVOUS FUNCTION. 
N the last section the mechanism of the ‘nervous system was 
considered. The modes and causes of its special development, 
and particularly the influences controlling the evolution of the 
cerebrum, now call for consideration. As already said, conscious- 
ness may, for all we know to the contrary, attend every nervous 
manifestation. But consciousness in that clearly defined and 
centralized condition which we call the psychical is the outcome ` 
of a long era of development through which the nervous mech- 
anism has attained a high degree of specialization. At first ex- 
cessively vague and faint it gradually grows stronger and more 
definite, until it reaches its ultimate in the vigorous, clearly de- 
fined and highly developed consciousness of man. 
This result has been in great part an outgrowth of the growing 
sensitiveness of animal life to external energy. In the lowest 
forms this sensitiveness is undoubtedly very slight. In the Pro- 
tozoa it is probable that touch is the only sense that has any 
degree of strength, though it seems evident that these animals are 
somewhat affected by influences emanating from substances at 
minute distances. Whether the vague sensations which attract 
the Protozoa to their food arise from physical emanations of the 
nature of smell, or from some heat or light influence, cannot well 
be determined. In many of the lower Metazoa there is no indi- 
cation of any superior sensory powers. In sessile forms, indeed, 
the powers may be yet lower. The sponge, for instance, may 
possess only the sense of touch, resident mainly in its cilia. The 
fixed polyps may possess no higher sensitiveness, though in the 
free forms, such as the Medusz, there is an evident display of 
more varied and delicate sensitiveness. 
Yet in all the lower forms of animal life one thing is evident. 
External energy does not force its way into the body in any very 
_ great quantity, and it is quite possible that every sensation may 
_ call forth a motor response. This, indeed, seems to be the case 
in yet higher forms of life. The sensations are so limited in 
number that there can readily be a motor response to every sen- 
_ sation, and there is no reason why there should be a change from 
