174 
CHARLES L. PARMENTER 
wide the body cavity. The folds of the viscera were pulled 
apart and the whole larva was plunged into the fixative. This 
secured immediate and uniform fixation. The operation requires 
less than a minute and the incisions are apparently painless, for 
the larva does not often struggle. 
2. The body walls, lungs, and viscera were removed from the 
body of the larvae before fixing, either in the field or at the 
laboratory. The peritoneum was fixed in situ on the body walls. 
Only normally inflated lungs were used, and these were ligated 
anteriorly before removal from the body to prevent them from 
collapsing. After fixing one or two hours, they were cut into 
two or more flat longitudinal strips and returned to the fixative. 
The mesentery, attached to the intestine, was spread out flat 
on a piece of glass and the whole immersed in the fixative with 
the tissue beneath. 
Fixatives 
The fixatives used were: 1) Flemming’s stronger solution, 
thirty hours; 2) Bouin’s solution, forty-three hours; 3) Bouin’s 
solution, to which was added 1^ grams of chromic acid crystals 
per 100 cc., twenty to twenty-four hours; 4) Hermann’s solution 
with two parts of osmic acid (Lee, ’13, p. 38) twelve to eighteen 
hours; 5) a solution of saturated picric acid 75 cc., formalin 15 
cc., glacial acetic acid 10 cc., urea crystals 2 grams, thirty to 
forty-three hours. The urea should be added gradually to the 
solution warmed to about 40°C., otherwise a precipitate is 
formed. 
It is a difficult matter to decide which solution gave the best 
fixation. The prettiest cells were fixed in Hermann’s and the 
chromic acid modification of Bouin’s fluid. However, the peri¬ 
toneum preparations of the osmic fixatives were a little thicker 
and less transparent than the others. If any fixative should be 
exclusively chosen, I believe it should be the chromic acid modi¬ 
fication of Bouin’s solution, because of its excellent fixation, 
convenience, and economy. 
The peritoneum was removed as follows: The two sides of 
the body wall were detached by an incision along the back 
