No. I.] HARDENING REAGENTS. 127 
34.2% ; while during the next 679 days it increased less 
than 4%. 
At the end of this time the specimen was well hardened, 
and the consistency was good; it was, however, a trifle 
brittle. 
The change in weight was determined by weighing the 
specimen from time to time, and the following were the 
conditions controlling the operation :— 
The balances ordinarily used responded to 0.01 grm. At 
times more delicate balances were employed. 
The specimen, as stated, was suspended in the fluid by 
means of a thread; this thread when dry, weighed, with little 
variation, .o5 grm. and gained almost 60% in weight after 
soaking in water or bichromate. The average hemiencephalon 
weighed when fresh about 56 grms., so that the weight of the 
thread would amount to less than 0.1% of this, which is insig- 
nificant for our purposes. 
Since, at each weighing, the specimen had to be removed 
from the fluid and then drained for a time, it became of interest 
to observe how rapidly it lost weight by drainage, and how far 
this operation could safely be carried. 
The principal conditions influencing the loss of weight by 
drainage are, of course, the time, the fluid and the temperature. 
This last was practically the room-temperature, and varied 
somewhat with the season, being in winter about 18-22° C. 
The specimens were put in a funnel and allowed to drain 
usually for seven minutes before weighing. To show the 
effect of drainage the following Table 2 is given. The 
specimens were removed and allowed to drip one minute 
before weighing at all; at the end of one minute the first 
weighing was made. They were then weighed at 2, 4, 6 and 
8 minutes after the first weighing and the percentage loss in 
weight calculated from the weight taken after one minute, as 
a basis. 
It will be noticed here that we give the percentage loss of 
specimens hardened in alcohol as well as those hardened in 
bichromate. 
The fuller observations on alcohol are stated farther along. 
