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.
Description:

Explanation of Plate XIX (figs. 1-7):

'Fig. 1. The supporting tissue or myelospongium of the spinal cord (copied from His).

Fig. 2. Portion of a section of the lining of the central canal in the region of the infundibulum of a puppy, to show how the original compact layers of epithelial cells spread out to form the substantia gelatinosa centralis.

Fig. 3. Section of the wall of the saccus vasculosus in the adult skate.

Fig. 4. Reproduction of Kölliker's drawing of the spinal cord of the embryo of the rabbit, to show how at this stage the dorsal part of the tube is free from the admixture of nervous material.

Fig. 5. Section of cord in chick (about 8 days) through the rhomboidal sinus to show the position of the groups of motor ganglia, and the manner in which a wedge-shaped mass of the original epithelial embryonic tissue remains on the dorsal side of the central canal free from admixture with nervous material.

Fig. 6. Appearance of this wedge-shaped dorsal mass of embryonic tissue in the more adult condition. The spaces formed by the nucleated meshwork are filled with a homogeneous gelatinous material.

Fig. 7. Section through the nervous matter forming the fimbria of a dog-fish, with its overlying membranous roof. The epithelial layer of the membranous roof is seen to be continuous with and to form the lining epithelium of the projections of nervous matter, while the pia mater as shown by the thin lines does not follow the couirse of the epithelial layer.

Fig. 8, Dorsal view of the medulla oblongata and cerebellum of a dog-fish. cb. worm of the cerebellum, l. the two lateral membranous pouches which form the roof of the commencing cerebellar hemispheres or fimbriae, d. membranous roof of the lVth ventlicle which is continuous with the two lateral membranous pouches.' (210-211)

 

Figs. 1-2 in text:

'The formation of this meshwork has been well described by His [note: 'op. cit'], who points out that it is formed by the modification of layers of epithelial cells of the same kind as those lining the central canal. The protoplasm surrounding the nuclous of the original cell thins out and elongates, forming long threads connecting together the nuclei which are now nearly denuded of their surrounding protoplasm. In Fig. 1, Pl. XIX I reproduce His' figure, which shows clearly the formation of this meshwork, to which he gives the name of myelospongium.

I also (Fig. 2, Pl. XIX) give a drawing of a portion of the substance lining the central canal in the neighbourhood of the infundibulum of a puppy, in which the limbs were fully formed and the groups of nerve cells in the cranial and spinal region is were well defined. It shows clearly the formation of the substantia gelatinosa centralis from the original layers of epithelial cells.' (192)

 

Figs. 1 and 3 in text:

'The same method of formation, with the same Structure, is found in the membranous portions of the brain already spoken of, such as the infundibular sacs of the skate and the inembranous enclosures of the fimbriae of the dog-fish, and the comparison of Fig. 3, Pl. XIX, which represents a section through a part of the saccus vasculosus of the skate, with Fig. 1 on the same Plate, shows that the membranous structure formed is in all cases the same in character as the myelo-spongium described by His, which was, as we have seen, formed from the walls of the saine embryonic tube. Especially instructive is the evidence given by the formation of the rhomboidal sinus in birds.' (197)

 

Figs. 4-6 in text:

'At first the embryonic tube is formed in the same manner in this part of the nervous system as in other places, so that Kölliker's picture of the cord of the rabbit, Fig. 4, Pl. XIX, may be used to illustrate the original relation between the nervous and non-nervous parts of the tube here as elsewhere. At a later stage we see as represented in Fig. 5, Pl. XIX, that the white matter of the cord remains separated in the dorsal region by the original layers of embryonic cells; the result being that in the course of growth this mass of embryonic tissue which is not invaded by nervous elements forms a wedge-shaped mass in between the nervous elements on each side.

This tissue is at first composed of the same kind of epithelial cells as those forming, the lining of the central canal, each cell possessing a well-defined nucleus in the midst of its protoplasmic contents so that at a period (about eight days) when the nerve cell groups of the anterior horn, the white matter of the cord and the central canal are all well formed, the appearance of a section through this region is as given in Fig. 5, Pl. XIX. Later on a peculiar degeneration takes place in these cells, which consists in the formation of a large quantity of gelatinous material which apparently, just as the fat globules in a fat cell, push the nucleus and the remainder of the protoplasm of the cell to one side, so as to give the appearance of a nucleated mesh-work, the interspaces of which are filled up with gelatinous material. This is represented in Fig. 6, Pl. XIX. At the same time in consequence of the large amount of gelatinous material, this wedge-shaped altered portion of the dorsal wall of the original tube presents the appearance in the adult bird of a jelly-like mass lying upon the spinal cord in this region.' (197)

 

Fig. 4 in text:

'According to the account given by Balfour, the white matter appears first in Elasmobranchs as a layer on the ventral and lateral parts of the spinal cord, but does not extend to the dorsal surface; at the same time the anterior white commissure is formed. About the same time two large bilateral ventral masses of nerve cells appear which are formed on the outer anterior part of the original thick walled tube as seen in Fig. 4, P1. XIX, so that at this time, before the dorsal coalescence of the walls of the canal to form the posterior fissure, the nervous elements are represented by a series of symmetrically situated bilateral ganglion masses connected together by longitudinal and transverse commissures, the whole being situated within the walls of, but ventrally to, the non-nervous tube already spoken of.' (198)

 

Fig. 5 in text:

'in crocodiles and birds at the very suirface of the lateral region of the cord a group of nerve cells exists which is as strictly metameric as the ganglion cells on the posterior roots of the spinal nerves. I have described this lateral group of cells in the cord of the crocodile in a former paper [note: 'Proc. Physiol. Soc. Dec. 12, 1886. This Journ. Vol. vii.']; and Fig. 5, P1. XIX illustrates their situation in the cord of the chick. ' (

 

Figs. 7-8 in text:

'In Fig. 8, Pl. XIX I give a dorsal view of the medulla oblongata and cerebellum of a large dog-fish to show the thin membranous roof of the 4th ventricle and its continuation into the two membranous lateral bags which overlie the fimbria. In Fig. 7, Pl. XIX I give the appearance of a transverse section through one of the fimbriae with its overlying membranous roof, to show how the epithelial lining of that roof does not follow the course of the pia mater, but passes into, blends with, and forms the lining of the nervous matter of the fimbria itself; as is also seen, proliferation of these epithelial cells appears to take place where the membranous bag, comes into close relation with the nervous substance.' (195)

 

Fig. 8 in text:

'This very formation of the worm of the cerebellum in the Elasmobranch produces of necessity the two lateral membranous folds shown in Fig. 8, P1. XIX. These in their turn become surrounded with nervous matter and then form the cerebellar hemispheres.' (208)