344 The Nissl’s Substance in the Bird Retina 
in size or shrunken, the cell body stained diffusely blue with methylene 
blue and the Nissl’s substance had completely disappeared. 
The changes in the cells by five minutes exposure to the concentrated 
electrical light he is inclined to interpret as merely due to heightened 
physiological activity, as they are completely repaired by a short rest. 
The complete disappearance of the Nissl’s substance together with 
swelling and shrinkage of the cell bodies and the nuclei consequent on 
longer exposure of the eyes, he regards as conditions of extreme fatigue 
or rather pathological. 
My own work was confined to the retin of the Brandt cormorant, 
Phalacrocorax penicillatus, and differed in method from that of Mann, 
Bach and Birch-Hirschfeld in this particular, that the retin from 
two different birds, one having been shut up in a darkroom, the other 
kept in the daylight, were compared, instead of the retine from the 
resting and the stimulated eye of the same animal. The cormorant 
was chosen because the ganglion cells in the retina of this bird are 
relatively large and very rich in Nissl’s substance. In all, the retine 
of fourteen birds were examined, seven in condition of rest and seven 
in condition of activity or fatigue. To secure prolonged absence of 
retinal stimulation the birds were placed in a dark room for twenty-four 
hours, at the end of which time they were decapitated, the anterior 
halves of the eyeballs and the vitreous humor removed and the eyes 
immersed in the fixing fluid. The dissections were done as rapidly 
as possible and by the aid of red light. To secure, if possible, maximal 
normal fatigue of the retinal elements an equal number of birds were 
confined in a room lighted with acetylene light during the night and 
the following day placed in a wire cage in the bright sunlight until 
2 p. m., when they were decapitated and the retine fixed in the same 
manner. During the night especially, but also during the day, the 
birds were prone to close the eyelids and assume a position as if resting 
or sleeping, but this they were prevented from doing, at least for any 
length of time, because they were constantly watched. 
The following fixing solutions were used, always at 38° C.: 
Sat. aq. Corrosive sublimate. .97 cc. ) Absolute aleohol 2... ..- 60 ce. 
Glacial acetic,....... 3cce. fj Ghilonokonmys erates cers 30 ec. }3. 
Sats aquenicrickaciden sec ICO?) Gs STE ETT oo ah ee 
Glacial acetic. -.-..- 5 ee. ATI CONOV fayesese op occrene choke evue 95 % 4, 
The retinze to be compared were fixed in the same fluid, kept the 
same lengths of time in the dehydrating alcohols, imbedded in paraftin 
side by side in the same block so as to be sectioned exactly the same 
