THE PERIPHERAL NERVOUS SYSTEM OE THE BONY FISHES. 
317 
mori)liological significance. The first spinal is obviously a fusion of two segmental 
nerves, possibly of more than two. 
The cranial nerves . — The four components found in the trunk are also found in 
the head, though in some cases strangely modified; and in addition to these there is 
a fifth, the acustico-lateral comiionent, which is not represented in any spinal nerve. 
There is no cranial nerve which contains all of these components, not even of the 
original four, and there is an obvious tendency toward the concentration of the fibers 
of each component so as to form a single system with a common center in the medulla 
oblongata, this being more marked in the case of the most highly specialized 
components and less so in those which are more feebly developed. 
Of the motor systems, the somatic motor is represented only by the eye-muscle 
nerves and the hypoglossus. Undifferentiated viscero-motor fibers of uncertain 
connections probably go out Avith the vagus. The motor roots of the X, IX, VIT, 
and V nerves probably represent highly specialized viscero-motor nerves developed 
in connection with the elaborate striated visceral musculature of the branchial arches 
and their derivatives. They appear to correspond to the viscero-motor fibers con- 
tained in the dorsal roots of the spinal nerves. 
Description of figure . — A diagrammatic aTcw of the sensory comi^ouents of the cranial nerves of 
Menidia, as seen from the right side. The diagram is based upon a projection of the- cranial nerves 
npon the sagittal plane made by reconstruction Ifom serial sections. The general cutaneous component 
is indicated by the wide cross-hatching, the communis component by aiarrow cross-hatching and the 
acustico-lateral is drawn in black. The following explains the reference letters : 
b. c. 1 toll. c. 5. Theflvc braucliialclef't.s. 
b. r. g. X. Thesaiiglia of tho four bran- 
chial rand of the vagus, the last one 
containing also the ganglion of the r. 
intestinalis. 
d. 1. g. Til. The dorsal lateral line gan- 
glion of the VII nerve. 
/. c. Fasciculus communis. 
Oas.g. Gasserian ganglion. 
gen.g. Til. Geniculate ganglion of the 
VII nerve. 
jug. g. Thegeneral cutaneousg.anglion 
of the vagus nerve— jugular ganglion 
of Shore and Strong. 
lob. X. The lobus vagi. 
71. 1. The olfactoi-y nerve. 
71. 11. The optic nerve. 
r. cut. dors. X. Eamus cutaneous dor- 
salis of the vagus. 
r.iiitest.X. Kamus intestinalis of the 
vagus. 
r. lat. X. Eamus lateralis of the vagus, 
r. oph. aup.Y. Eamus ophthalmicus su- 
perlicialis trigemini. 
r. oph. sup. Til. Eamus ophthalmicus 
superficialis facialis, 
r. of. Eamus oticus. 
r.pal. Kamus jialatinus facialis. 
r.rec. Til. Eamus lateralis accesso- 
rius, or r. recurrens facialis. 
r.st.X. Eamus supratemiroralis vagi. 
r. Til i>1. Eamus pretreraaticus faci- 
alis. 
sp. T.t. Spinal Y tract (“ascending 
root of the trigeminus '). 
t. a. Tho tubercnlum acusticum. 
t. hm. Truncus hyomandibularis of the 
facial nerve. 
t. inf. Infraorbital trunk, contaijdng 
the r. mandibularis Y, the r. maxil- 
laris V, and the r. buccalis VII, to- 
gether with communis fibers. 
Till. The eighth nerve. 
V. 1. g. TII. The ventral lateral-line 
ganglion of the A^II nerve. 
