482 THE SALIVAR Y 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 lingual 

 nerve to run to the sublingual and submaxillary plexuses consist in 

 very large part of small fibres, about 2 //, to o'o /j, in diameter, 1 but a few 

 larger up to 8 or 10 ^ are also present. In the plexuses the number of 

 medullated fibres decreases, and the number of iion-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. Eahn (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. Heidenhain, Arch. f. Anat. u. PhysioL, Leipzig, 1883, Supp. Bd., S. 158 ; 

 Gaskell, Journ. PhysioL, Cambridge and London, 1886, p. 29. 



2 Moussu, Arch, de physiol. norm, ctpalh., Paris, 1880, p. 68. (Cf. this paper also for 

 secretory nerves of horse and pig.) Eckhard, Centralbl. f. PhysioL, Leipzig u. Wien, 

 1893. 



3 For the method of dissection for experimental purposes, see Heidenhain, Hermann's 

 "Handbuch der Physiol.," Bd. v. Th. 1, S. 38. 



4 Ludwig, Ztschr. f. rat. Med., 1851, N. F., Bd.i. S. 255 ; Rahn, ibid., S. 285; Schiff, 

 Arch. f. physiol. Heilk., Stuttgart. 1851, Bd. x. S. 581 ; Bernard, "Lecons sur la physiol. et la 



