600 
F. H. EDGEWORTH. 
of the fifth nerve in the rabbit and dog gave the same results 
in regard to the entry of sensory fibres into the motor root, 
and the constitution of the ramus lateralis, ramus medialis, 
and mylohyoid nerve. 
These observations show that in Macacus, man, rabbit and 
dog, the muscles innervated by the fifth cranial nerve receive 
afferent fibres, which originate in the Glasserian ganglion, and 
pass into the motor root. The motor and ganglionated 
afferent nerve-fibres of the ramus lateralis have a simple 
direct path ; those of the ramus medialis and of the mylo- 
hyoid nerve have, for a space, a double course, being divided 
by the ramus posterior into two groups which again unite to 
form those nerves (fig. 21). The reasons for this curious 
path are doubtful — the phenomena suggest a downward 
growth of the ramus posterior occurring later than that 
of the muscular branches, and splitting up those destined for 
the ramus medialis and mylohyoid nerve. This actually 
occurs in rabbit embryos — the mylohyoid nerve is present in 
the mm. stage, the rami medialis and lateralis are developed 
in the 8 mm. stage, the ramus posterior not until the 9 mm. 
stage. I could not obtain embryos of Macacus, man or 
dog. 
Information as to the end-organs of the afferent nerve- 
fibres of the masticatory muscles is as yet scanty and incom- 
plete. Cipollone has stated that muscle-spindles are present 
in the masseter and pterygoid muscles. 
Mesencephalic Root of the Fifth Nerve. — May and 
Horsley (’10) showed that practically all the axons of the 
globular cells of the mesencephalic root of the fifth nerve 
leave the pons by the motor root of that nerve, that destruc- 
tion of it does not cause either motor or sensory loss, that 
stimulation of the root on the cut surface of the mesence- 
phalon produces no effect on the muscles of mastication unless 
the excitation spreads to the pontine masticatory nucleus, 
and “ that avulsion of the peripheral branches of the infeifior 
division causes chromatolysis in the mesencephalic root cells, 
a result suggesting that these axons run in the peripheral 
