482 THE SALIVAR V GLANDS. 
ganglion, but it is probable on general grounds that they are not con- 
nected with the nerve-cells of this ganglion. 
The nerve-strands which leave the chordo-lingual and the lintrual 
nerve to run to the sublingual and submaxillary plexuses consist in 
very large part of small fibres, about 2 p to 3 -5 fi in diameter, 1 but a few 
larger up to 8 or 10 /x are also present. In the plexuses the number of 
medullated fibres decreases, and the number of non-medullated fibres 
increases in passing towards the periphery. The axis-cylinder pro- 
cesses, then, of most, if not of all, the peripheral nerve-cells are non- 
medullated fibres. 
The large nerve-fibres may occasionally be seen to divide. They are 
probably sensory fibres for the gland arising from the fifth nerve. Some 
of the small fibres may also be sensory. 
Cranial nerve-fibres to the parotid and orbital glands. — The 
course of the secretory and vaso-dilator fibres to the parotid gland varies 
in different animals. 
In the dog they arise from the ninth nerve ; they run — as Jacobson's 
nerve — across the tympanic cavity over the promontorium forming part 
of the tympanic plexus. From the tympanic cavity they proceed to the 
small superficial petrosal and otic ganglion, and thence to the auriculo- 
temporal branch of the fifth nerve, and so to the parotid gland. 
In the sheep and ox the origin of the secretory fibres from the 
medulla is not known. They run in the buccal branch of the fifth nerve, 
instead of in the auriculo-temporal, leave this at the anterior end of the 
masseter muscle, and run backwards to the parotid gland along the 
duct. 2 
There are no experimental investigations on the place of connection 
with nerve-cells of the cranial fibres to the parotid gland, but it has 
been supposed that this connection occurs in the otic ganglion. No 
ganglion cells have been described in the parotid gland itself. 
The secretory fibres for the orbital gland of the dog run in the 
buccinator branch 3 of the fifth nerve, and this is all that is known of 
their course. 
Historical.— The history of the discovery of the course taken by the 
cranial secretory fibres 4 may be briefly summarised as follows : — 
In 1851, Ludwig discovered in the dog secretory fibres for the sub- 
maxillary gland in the lingual branch of the fifth nerve. Rahn (and Ludwig) 
obtained in the rabbit secretion from the parotid, and sometimes from the sub- 
maxillary gland, on stimulating certain cranial nerve roots, after removing the 
brain. They found the effective nerve-roots to be those of the seventh and of 
the fifth, but their experiments do not show satisfactorily that the secretory 
fibres leave the medulla by way of these nerve roots. 
Bernard showed that the secretory fibres of the submaxillary glands came 
from the chorda tympani and so from the facial nerve. That the chorda 
tympani had some connection with the flow of saliva from the submaxillary 
1 Of. Heidenliain, Arch. f. Anat. u. Physiol., Leipzig. 1883, Supp. Ed., S. 158 ; 
Gaskell, Journ. Physiol., Cambridge and Loudon, 1886, p. 29. 
- Moussu, Arch, dephysiol. norm, ct path., Paris, 1880, p. 68. (Cf. this paper also for 
secretory nerves of horse and pig.) Eckhard, Ccntralbl. f. Physiol., Leipzig u. Wien, 
1893. 
3 For the method of dissection for experimental purposes, see Heidenliain, Hermann's 
"Handhueh der Physiol.," Bd. v. Th. 1, S. 38. 
* Ludwig, Ztschr. f. rat. Jin/.. 1851, X. F., Bd. i. S. 255 ; Eahn, ibid., S. 285; Schiff, 
Arch. f. jihysiol. Heilk. , Stuttgart, 1851, Bd. x. S. 581 ; Bernard, " Lecons sur la physiol. et la 
