722 Growth and Development. (July, 
cles, which seem to collect the vibrations. In fact all the special - 
senses make use originally of conditions which arise in the 
body as necessary or occasional results of its action, and which 
are subsequently developed by the incessant play of external 
force, into definite sense organs. 
In the secondary development of nerves the incessant inflow of 
motor impressions renders some check important, since, as the 
sensitiveness of the body increases, a muscular response to every 
sense impression would totally exhaust the vital energies. This 
check takes place wherever the nerve fibers are reduced in size, 
the energy dissipating from that point, as electric energy dissi- 
pates in the form of heat when its conductor is too much reduced 
in size. This checked energy becomes growth force at the poss 
of its dissipation ; and nerve cells, aggregating into ganglia, ap- 
pear at these points. In the higher animals a special region for | 
the checking of sensory force is developed, the congeries of nerve — 
cells there produced constituting the brain. The growth of the 
brain increases as sensitiveness increases and as the muscular 
response to,impression is hindered, while the energies which out- 
flow into the brain are stored up in some unknown manner, whose | 
results we call the mind. : 
_ Thus external impression appears to yield several successive 
kinds of organic results. It first instigates growth at the imme 
diate point of contact, and surface protrusions geese ae 
reside the chief motor and sensory power. Secondly, pore’ 
nal energy forces its way inward, by conductive channels, 
discharged at internal points. Growth of muscular ae 
place at these points of discharge, and of sensory wea acked at : 
points of reception. Thirdly, the inflowing energy 15“ ie 
certain points on the nerve fibers, and instigates the grow! re 
nerve cells at those points. Fourthly, the energy di special : 
the principal ganglion causes the development of pe w 
organism for its reception and organization. pe but arè : 
organized we call the mind, its substantial basis the | aout 2 
ignorant of the nature of either. Such seem to be the s o atly | , 
results of external force impact. The other organs ssid ce the 
derived. The functions of digestion and excretion iar nday 
growth results through pressure impressions pas the vasculat 
system of nerves and muscles; the development muscles aa 
organs is a necessary accompaniment of that of the Wr 
