2 JouURNAL OF CoMPARATIVE NEUROLOGY. 
I. TECHNIQUE. 
The white rat was used for the present work. Since the 
nerve cells are rapidly altered after death and also undergo 
changes in old age—as shown by Hopcr'—care was taken to 
use material from animals freshly killed, and mature, but not 
senescent. 
White rats, between 100 and 150 grams in body weight, 
were employed. Specimens of this weight are in the prime 
of life. 
After being chloroformed, the animal was dissected and 
the ganglia removed. These were preserved separately in the 
following fluids. The preserving fluids, as well as staining 
agents, which have been recommended by previous authors are 
marked by the author’s name above the formula. Fluids which 
are not named were devised by the writer : 
I. Carnoy's Flud. 
Alcohol A 5 < 60 cc 
Chloroform : 5 30 cc 
Glacial acetic acid . 10 cc 
2. Ewing's Fluid. 
Mercuric chloride, sat. sol. in 5% Formalin. 
3. Graf's Fluid. 
Oxalic acid 80% ‘ 4 vol. 
Alcohol 95% : 3 vol. 
Chromic acid 1% . 3 vol. 
4. Lenhossck’s Fhud. 
Corrosive sublimate, aq. sat. sol. 
5.  Gtlson’s Khud. 
Nitric acid of 46° strength ‘ 78 cc 
(This would be sp. gr. 1.456 or 80% nearly.) 
Glacial acetic acid : ; 22 cc 
Corrosive sublimate, aq. sat. sol. 50 cc 
60% alcohol . ° . - 500ce 
Distilled water “ . a) AACE 
1 Hopce—Changes in ganglion cells from birth to senile death. Observa- 
tion on man and honey bees. /ourn. Physiology, Vol. 17, ’94. 
