350 Proceedings of the Royal Society of Edinburgh. [Sess. 
The visual sensory conduction path consists of the following stations : — 
< 
Rods Outer Inner Ganglion Decussation. Stations Cortex, 
and nuclei. nuclei. cells. in thalamic 
cones. region. 
The rods and cones and outer nuclei may be looked upon as true 
peripheral neurons. The inner nuclei may be looked upon as the homo- 
logues of the sensory nerve fibres. The ganglion cells are central and are 
the homologues of the cells of the medullary nucleus of the sensory chains 
of other special sense mechanisms. 
Compare the gustatory sensory path as given below : — 
1 — 
Taste Taste Medullary Decussation. Thalamic Cortex, 
cell. fibre. centre. station. 
Mode of Experiment— The experiments were performed on rabbits. 
The duration of the experiment varied from 24 hours to 38 weeks. 
Histological investigation was by the Held-Nissl method. 
The results of the investigation may be tabulated as follows : — 
Tabulated Results. 
Exp. i. 
Exp. ii. 
Exp. iii. 
Exp. iv. 
Exp. v. 
Exp. vi. 
Exp. vii. 
Exp. viii. 
24 hours. No change in retina. 
48 hours. Slight blurring of Nissl’s granules in the ganglion 
cells. Outer neurons normal. 
48 hours. Same as ii. 
72 hours. Slightly increased blurring of Nissl’s granules. 
Outer neurons normal. 
4 days. Much the same as iv. 
7 days. Some shrinking of ganglion cells. Nissl’s granules 
often dust-like. Slightly diffuse staining of protoplasm. 
Outer neurons normal. 
8 days. Diffuse staining more marked. Granules often 
dust-like. Outer neurons normal. 
3 weeks. Ganglion cells much shrunken. Nissl’s granules in 
bSad-like rows, or in form of very fine dust. Outer 
neurons normal. 
