Cited by W.H. Gaskell, 'On the Relation between the Structure, Function, Distribution and Origin of the Cranial Nerves; together with a Theory of the Origin of the Nervous System of Vertebrata', Journal of Physiology 10 (3) (1889), pp. 153-212.
Tags: osmic acid
Description:

Explanation of Plate XVII (figs. 1-4):

'The sections are all carefully drawn from osmic acid preparations of the nerves of man.

Fig. 1. Transverse section of rootlet of IIIrd cranial nerve to show degenerated ganglion. (Zeiss A, Oc. 4.)

Fig. 2. Three transverse sections of IVth cranial nerve. (Zeiss A, Oc. 2):

a. Section near exit of nerve from valve of Vieussens, showing degenerated tissue arranged so as to form a sheath around the functional medullated nerve-fibres.

b. Section of nerve farther away from point of exit, showing the formation of the degenerated galglion.

c. Section of nerve peripheral to the ganglion. The degenerated tissue has almost entirely disappeared.

Fig. 3. Transverse section of VlIth cranial nerve to show degenerated ganglion. (Zeiss A, Oc. 2.)

Fig. 4. Longitudinal section of a rootlet of IlIrd cranial nerve to show the structure of the degenerated material. (Zeiss D, Oc. 2.).' (209)

 

Figs. 1-2 in text:

'In Pl. XVII, Fig. 2, I give three sections of the IVth nerve selected out of the whole series. The section (2a) is through the root of the nerve close to its exit from the valve of Vieussens, and it shows that the nerve fibres are surrounded by a thick sheath of peculiar connective-tissue-like material; while section (2c) taken more towards the periphery shows that this sheath of peculiar tissue no longer exists. An examination of the sections between 2a and 2c shows that the manner of disappearance of this thickened sheath is very peculiar, it does not remain on the outside of the nerve fibres but forms roundish masses of the same -peculiar material in between the nerve fibres themselves as is seen in (2b), so that the sections with a low power possess a remarkable resemblance to a section through a ganglion. At the peripheral side of this ganglion- like formation these round masses of fibrillar-like material cease somiewhat abruptly and the sections appear as in 2c. Again in the IlIrd nerve the same formation is seen; here we have a nerve composed of a great numnber of rootlets and the sections show that the ganglion-like structure makes its appearance on the separate rootlets before they join together to form the conjoint root. Very striking indeed is the sight of a number of these rootlets each presenting in a greater or less degree the appearance represented in Fig. 1, PI. XVII. Here too we see another point of resemblance between this structure and a spinal ganglion. In the latter it is of common occurrence to find that the formation of the ganglion has thrown many nerve fibres out of their previously parallel course, so that on transverse section of the ganglion many fibres are cut in a more or less longitudinal direction; the same deviation is found, as is seen in Fig. 1, in many of the large, fibres of the IIIrd nerve, which are thrown out of their direct course in consequence of the formation of these rounded fibrillar masses in a way precisely similar to what occurs in the spinal ganglion.' (167)

 

Fig. 2 in text:

'In the Elasmobranch, as for instance the dog-fish... we find in the infundibular region a membranous sac known as the saccus vasculosus, the membranous roof of the 4th ventricle is more extensive than in the mammal, the choroid plexuses are very conspicuous as is shown in the diagram Fig. 2, P1. XVIII.' (194)