342 The Nissl’s Substance in the Bird Retina 
studied also the cells in the sympathetic ganglia, in the spinal cord, in 
the cerebral cortex and in some of the nuclei of the midbrain. These 
are his conclusions : 
“1. During rest, several chromatic materials are stored up in the 
nerve cell, and these materials are used up by it during the perform- 
ance of its function. 
“2. Activity is accompanied by an increase in size of the cells, the 
nuclei and the nucleoli of sympathetic, ordinary motor and sensory 
ganglion cells. 
“3. Fatigue of the nerve cell is accompanied by shriveling of the 
nucleus and probably also of the cell, and by the formation of a diffuse 
chromatic material in the nucleus.” 
Of his observations on the retina he says: ‘In four dogs which were 
allowed to run about for twelve hours with one eye covered up while 
one eye was exposed, and the brains and retine of which were fixed by 
injecting HgCl, from the aorta, I notice in the retina kept in darkness 
that the nuclei of the rods are very rich in chromatin, the individual 
chromatin segments being globular, spherical externally, and facetted 
where in contact with one another, while in the exposed eye the chro- 
matin segments are greatly shrunken and quite stellate. The nuclei of 
the ganglion cells of the dark retina are smaller than those in the exposed 
retina, and in the latter the nuclear hyaloplasm is no longer stained with 
methyl blue.” 
This is all he says of his work on the retina. He does not mention 
any changes in the Nissl’s substance in the cells of the ganglionic and 
the bipolar layer; and the figures (Plate I, figs. 6 and 7) show only the 
changes in the size and contour and in the amount of chromatin in the 
nuclei of the rods and cones and the bipolar cells. But in the three 
general conclusions the cells of the retina are evidently included. 
Bach (1895)° repeated Mann’s experiments on the retina of dogs 
with some modification, but was unable to verify the latter’s findings on 
any point. Of the Nissl’s substance Bach says: ‘“* Weder in der Menge, 
noch in der Anordnung, der Form der firbbaren Plasmaschollen ... . 
konnte ich constante, markante principielle Unterschiede zwischen be- 
leuchteten, verdunkelten, normalen Netzhiuten entdecken.” 
Pergens (1896)° found that in the retina of fishes (fixation in nitric 
acid and staining with methylene blue or the Ehrlich-Biondi stain) 
°Bach: Zur feinen Anatomie und Pathologie der Ganglienzellen der Retina. Trans. 
VIII Internat. Ophthalm. Congress, Edinburg, 1895. Cited from Birch-Hirschfeld. 
®Pergens: Action de la lumiére sur les elements nerveux de la rétine. Central- 
blatt fiir Physiologie, 1896, X, 8. 274. 
