22 Comparative Neurology. [January, : 
the so-called “space sense” of the human labyrinth). Prof — 
Mayer also announced that the terminal auditory nerve-fibers 
vibrate half as often in a given time as the membrane of the tym- — 
panum and the ossicles. 
In these instances there is a direct derivation of an auditory — 
from the special tactile which, in turn, was evolved from the gen- — 
eral tactile sense, and does not seem to be lost, even in man, asa 
property of sensory nerves. : 
A heat sense system of nerves developed from pigment ter-_ 
minals, by further elaboration could become ocelli and finally — 
eyes. 
A special series of nerves for heat appreciation would have — 
necessarily a general distribution throughout the body, to viscera as 
well as to more external peripheries. 
Nervous tissue appears at the same time as muscular, and © 
affords a better path or course of less resistance for the molecu- — 
lar vibrations from without. The muscular is a definitely located — 
expression of what previously belonged to all parts of the animal, 
contractile ability or motility for assimilative purposes. 
is assimilative faculty is essentially prehensile, and in the — 
word prehension we may grasp the idea of a differentiation of © 
such faculties as respiration, locomotion, deglutition, etc. 2 
Carrying the comparison from Protozoa to man, all that man — 
does or may hope to do has for its basis the single fundamental, — 
though widely differentiated faculty of prehension. : 
Jaws and arms are prehensile, clearly. Ribs are ssechecaa in: 4 
the sense that they assist in prehension of oxygen (food) for the — 
lungs, morphologically and less physically in man, while in — 
Ophidia the ribs are locomotory prehensile, direct. ; 
Legs are prehensile directly in quadrumana, and in man in car- 
rying him over ground in search of food. : 
As mentioned, the next step in development of the nervous — 
system is when the ingoing general impressions become special- _ 
ized and a secondary ganglion appears upgn a sensory strand of © 
the primary, which signifies that from among the general impres- ; 
sions some one sense, as sight, is being specialized. This is out- 
wardly evidenced by formation of ocelli or gee (leech), which ‘ 
require a special projection. a 
By quantitative increase multiple eyes may form (leech) and 
these become united into bilateral organs (pyramidal fusion in 
crayfish). s 
