666 HENRY H. DONALDSON 
At this time any necessary correction in the body weight was 
made by subtracting from the initial weight, the weight of the 
ova or of undigested food distending the stomach. These were 
the only two corrections made to the body weight. The body 
weights of the females are always given without the ova. 
After evisceration. the brain was exposed throughits entirelength 
and the spinal cord exposed as far down as the III nerve. With 
spring compasses, the length of the brain from the tip of the olfac- 
tory bulbs to a point midway between the tip of the calamus scrip- 
torius and the level of the III nerve =(origin of II nerve) was 
taken. This was recorded to the nearest 0.1 mm. = (brain length) 
The olfactory nerves were next cut through with a very fine scis- 
sors, and in the same manner a section was made between the 
tip of the calamus scriptorius and the III nerve, 7.e., the level of 
the emergence of the II nerve. The choroid plexus over the fourth 
ventricle was removed and then the brain was raised from be- 
hind forwards on a narrow lifter, and the nerve roots severed as 
close to the brain as possible. 
If the hypophysis was still attached to the brain, it was removed 
and the remaining mass at once placed in a closed weighing 
bottle and weighed to 0.1 milligram =(brain weight). 
Similarly the spinal cord was exposed through its entire length 
and the conus just caudad to the XI nerve laid bare. With the 
spring compasses the length from this point to the level at which 
the cord had been severed from the brain was measured and re- 
corded to the nearest 0.1 mm. =(cord length). The cord was then 
seized just below the conus with a fine forceps and raised so that 
the nerves could be clipped away close to the cord. The mass of 
the cord, thus deprived of nerves, was placed in a closed weighing 
bottle and at once weighed to 0.1 milligram = (cord weight.) 
Both parts of the central nervous system were then dried at 
90-95° C. for a week and reweighed. From these data, the 
percentage of water in the brain and in the spinal cord was de- 
termined to 0.1 per cent =(percentage water, brain) = (percent- 
age of water, spinal cord). 
For the present investigation, the foregoing determinations 
represent all that are necessary. 
