156 J. B. JOHNSTON, 
2. Centers of sensory Nerves. 
Before taking up the sensory nuclei I shall make a brief survey 
of the cranial nerves in fishes, in order to identify the several roots 
and their central nuclei and to determine with certainty the homo- 
logous centers in various groups of fishes. To interpret rightly the 
structures of the central nervous system it is necessary to know 
in what nuclei the several nerve components, as determined by their 
peripheral distribution, have their central endings. It is fortunate 
for the study of lower brain morphology that the study of the cranial 
nerves is so far advanced that there is now no reasonable doubt 
as to any important question of fact in the distribution of the various 
components of the cranial nerves. A review of the literature of the 
nerves will give a foundation on which to base definite conclusions 
in the interpretation of the medulla and cerebellum. 
General cutaneous components. — There is general 
agreement among authors -that general cutaneous sensation is me- 
diated by the trigeminus or some part of it. The nerve which 
in the later literature has come to be regarded as the V proper is 
described by Stannius (49) as the first root of his V—VII complex, 
and contains sensory and motor fibres. The sensory fibggs innervate 
the skin on the dorsal surface of the snout in front of the eye, the 
skin around the nasal pits, and on the upper and lower jaws. Along 
with these run fibres from his dorsal (third) root which innervate 
the slime canals. Whit this statement of STANNIUS, applying to 
fishes in general, the descriptions of JACKSON and CLARKE (76) 
for Echinorhinus, of Ewart (’89) for Laemargus, of Pınkus (95) for 
Protopterus, of COLE (96b and ’98b) for Chimaera and Gadus, and of 
C. J. Herrick (99) for Menidia, are in substantial agreement. The 
details of the distribution and endings of the general cutaneous 
fibres have been worked out for fishes by HERRICK (1. c.), and by 
STRONG (95) for the tadpole. Two results of STRONG’s study are 
of interest here: first, he (apparently) regards the V as wholly general 
cutaneous; second, he has shown that a large part of the general 
cutaneous fibres run in other nerves besides the V, namely the IX 
and X. These fibres had been noted by MayseEr (81) in Teleosts, 
and by OSBORNE (’88) in Cryptobranchus. They have since been 
described by KinessBury (97) for several fishes and by HERRICK 
for Menidia. These general cutaneous fibres in IX and X, however, 
enter the same central tract as those belonging to the V, namely the 
