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BULLETIN OF THE UNITED STATES FISH COMMISSION. 
Some years ago I formulated the following definition of such a functional system 
of neurones, with special reference to the peripheral members of the system: 
The sum of all the nerve fibers in the body which possess certain physiological and morphological 
characters in common so that they may react in a common mode. Morphologically each system is 
defined by the terminal relations of its libers, by the organs to which they are related peripherally, 
and by the centers in which the libers arise or terminate. The fibers of a single system may appear 
in a large number of nerves repeated more or less uniformly in a metameric way (as in the general 
cutaneous system of the spinal nerves), or they may all be concentrated into a single nerve (as in the 
optic nerve). 
Now, if we add to this the secondary paths related to the primary central end 
stations referred to above, and the chief reflex arcs directly associated therewith, we 
shall have a picture of the system in its entirety. 
The functional system with which we are especially concerned in the present 
research is that known to comparative anatomy as the communis system, including 
(1) unspecialized visceral sensory fibers ending free in the mucous surfaces of various 
viscera without special sense organs — probably phylogenetically the more primitive 
elements — and (2) specialized sensory fibers always ending in connection with highly 
differentiated sense organs in the mouth, pharynx, lips, or outer skin, known as taste 
buds, terminal buds, or end buds, and in general serving the function of taste. These 
specialized elements are probably of more recent phylogenetic origin than the first 
group, and the term “gustatory system” will be used to designate these organs, wher- 
ever placed on the body surface, together with their nervous pathways toward and 
within the brain. In other words, the gustatory system is that portion of the com- 
munis system of neurones which serves the sense of taste, as distinguished from 
those communis neurones which serve less highly specialized visceral sensations. 
These two groups of fibers can easily be distinguished peripherally of the brain, 
but centrally they have not as yet been successfully analyzed. Hence in treating of 
the central gustatory path we can not be sure that we do not include the unspecialized 
visceral system also. Hut since in some fishes the gustatory fibers preponderate 
many fold over the unspecialized fibers of the communis s}rstem, there is no 
ambiguity arising from this central confusion of the two elements so far as the 
gustatory system is concerned, since the secondary paths as clearly traceable in these 
fishes must be made up chiefly of gustatory fibers. 
The central gustatory path is not definitely known either in man or in any other 
vertebrate, so far as shown by the available literature. I have therefore studied with 
some care the brains of some fishes in which this system is enormously developed, in 
the hope that they would throw light on this unsolved problem of vertebrate anatomy. 
And in this I have not been disappointed, though my study of the central paths is not 
yet sufficiently advanced for publication. 
As intimated above, sense organs belonging to the communis system and pre- 
sumably serving the function of taste are found in the mouths of all fishes (“ taste 
buds”). They are frequently found upon the lips, and in some cases they are found 
likewise plentifully distributed over extensive areas of the outer skin of the head 
and trunk. In this latter case they are commonly termed terminal buds or end buds 
(End/cnospen, Becherorgane , of the Germans). They must in all cases be sharply 
distinguished from the neuromasts, or organs of the lateral-line system (German, 
