66 Drxon—On the Development of the Branches of the Fifth Cranial Nerve in Man. 
(see page 58). This agrees exactly with what may be observed in the rat, in 
which animal also, the nerve of Jacobson grows out from the petrous ganglion of 
the glosso-pharyngeal nerve. The fact that these connecting nerves are not 
branches of the trigeminal, but of the facial and glosso-pharyngeal, renders it 
improbable that through them taste impressions are transmitted to the fifth 
nerve, and so to the brain. 
From analogy with what is known for other nerves we would expect that 
impulses, of whatever kind they may be, transmitted by these connecting nerves, 
would pass to the brain by way of the facial and glosso-pharyngeal nerves. It is 
true that Penzo* considers that he has proved, from dissections of the nerves in the 
adult, that the chorda tympani and the great superficial petrosal nerves contain 
fibres derived from the fifth nerve. If this is so, these fibres must grow out from 
the fifth nerve into the course of the Vidian and chorda tympani at a later period 
than the stage represented by Ru. (5th week). Whether fibres actually do grow 
back from the fifth nerve, into the course of the seventh and ninth nerves, would be 
very difficult to determine, and if such fibres exist and convey taste impulses into 
the path of the trigeminal, their late formation is a remarkable fact. On the other 
hand, since the facial and glosso-pharyngeal nerves are, at all events, in part 
developed as sensory nerves, and since the ganglia present in connection with 
them in the adult, possess the characters of ganglia on posterior nerve roots, there 
is no reason for denying them sensory branches. 
Embry ologically, the nerve supply of the organs of taste, appears to be derived 
from the facial and glosso-pharyngeal nerves alone, since the lingual admittedly 
in itself contains no taste fibres. 
In the fact that the Vidian and the nerve of Jacobson, in addition to the 
chorda tympani, are not branches of the fifth nerve, we have an example of 
the tendency exhibited by the posterior cranial nerves, to turn upwards and 
trespass beyond their proper areas of distribution, as has been illustrated by 
Professor His.t 
* «Ueber das Ganglion geniculi und die mit demselben zussamenhingenden Neryen,’’ Anatomischer 
Anzeiger, 1893, p. 738. 
+ ‘‘Die Morphologische Betrachtung der Kopfnerven,” Archiv fir Anat. und Phys. Anat. Abth., 
1887, p. 449. 
