766 
SUMMARY OF CURRENT RESEARCHES RELATING TO 
of the peripheral protoplasmic prolongations of all the optic nerve-cells 
of the median layer. Among these two sets of terminations nerve-cells 
with a descending cylinder-axis are to be seen. In some cases the 
cylinder-axis is short, and ends in the superficial parts of the median 
layer, while in others it is long, and is sometimes continuous with a 
central optic fibre of the internal layer. The layer of retinal fibres 
corresponds to the layer of olfactory fibrils of the olfactory bulb of 
Mammals with some slight histological difference. 
The second layer, that of the optic nerve-cells, is formed essentially 
of cells, all of which send out protoplasmic prolongations among the 
retinal ramifications of the outer layer. The nervous prolongation of 
the cells with a long cylinder-axis is sometimes continued into the 
internal layer, where it becomes a central optic nerve-fibre ; in other 
cases it passes into the outer layer where it becomes a peripheral optic 
fibre, and, probably, penetrates as far as the deep layers of the retina. 
The nerve-cells with short cylinder-axes belong to one of two groups, 
according as their nervous prolongation is peripheral or central. 
The layer of central optic fibres is formed essentially of nerve-fibres, 
the origin of which is double. Sometimes they arise from optic nerve- 
cells of the median layer, just as the nerve-fibres of the inner layer of 
the olfactory bulb arise from the ventral cells ; in other cases their origin 
is unknown, and they terminate in the two outer layers. Eamon y 
Cajal admits the existence of similar fibres in the olfactory bulb of 
Mammals, though the author was unable to find them. 
From the fact that the fibres of the optic nerve end freely in the 
outer layer of the lobe we may draw the important conclusion that, 
contrary to what has been hitherto supposed, the optic nerve does not 
have its origin, but only its termination in the optic lobe. 
Spinal Cord and Ganglia of Pristiurus-Embryos.* — Prof. M. v. 
Lenhossek, using Golgi’s and Ehrlich’s methods, has corroborated the 
well-known interpretation of the nervous system which is associated 
with the names of Kupffer and His. The axis-cylinder process of a 
motor anterior-horn cell passes from the cord as a peripheral motor 
fibre, preserving its individuality and its character as the product of a 
single cell even to its end on a muscle. In the spinal ganglion there is 
essentially but one kind of cell — a typical bipolar element — of whose 
processes one may be followed in the cord in the course of the sensory 
root, while the other extends as a smooth delicate fibre to its terminal 
ramification between epidermic cells. There is no doubt that the 
posterior root-fibres, like the peripheral sensory fibres, arise from spinal 
ganglion-cells. The established histological facts are, according to 
Lenhossek, quite fatal to Beard’s recent conclusions on the histogenesis 
of nerve. 
7. General. 
The Living Organism.f — Sig. F. Ardissone, from the standpoint of 
one who is not ashamed of Platonic philosophy, enters a protest against 
a materialistic conception of organisms. Although his criticisms of 
* Anat. Anzeig., vii. (1892) pp. 519-39 (19 figs.). 
f ‘ L'Organismo vivente considerate) nella sua essenza e nella sua origine,’ Varese, 
1892, 8vo, 24 pp. 
