PHYSIOLOGY OF DIGESTION IN BLATTIDAE 375 
In my experiments I used animals which had been starved 
two weeks to be sure no residue of fat was in the cells. As a 
matter of fact, no intracellular fat could be found after six days’ 
starvation. The animals were fed a paste of olive oil and pow- 
dered sugar, and were dissected and fixed in Flemming’s fluid 
after varying lengths of time, prepared by the paraffin method, 
and stained with acid fuchsin, In some cases Flemming’s fluid 
was injected into the body cavity, but as this method gave no 
better results it was discontinued. In one series of experiments 
in fat breeding the following conditions were found in the cells 
of the crop: eight hours after feeding, small amounts of fat in the 
cells; after sixteen hours, small amounts; after twenty-four hours, 
moderate amounts; after thirty-two hours, large amounts; after 
forty-eight hours, maximum amounts, with many large globules 
of fat:in the cells and in some cases the cells entirely black with 
fat to exclusion of all cell parts; after seventy hours, large 
amounts, the globules large and often seemingly in process of dis- 
solution (figs. 3 and 4). At later stages more or less fat is pres- 
ent in the lacunae behind the epithelium. Controls were tried 
with a paste of sugar and mineral oil, the latter oil being indi- 
gestible, but without getting pictures of fat globules in the 
cells. 
The following experiment also has an interest in this connec- 
tion. <A cockroach was fed a large amount of a paste of olive oil, 
sugar, and blue litmus powder, then its body cavity was entered 
and its crop ligated posteriorly. After forty-eight hours the ani- 
mal was killed and the alimentary canal preserved. The crop 
showed a red content anterior to the ligation and this part was 
preserved in Flemming. Histological examination of trans- 
verse sections revealed many globules of fat in most of the cells. 
This fat had been absorbed here, and prepared for absorption by 
the crop secretion, for the stomach secretion could not have gotten 
here past the ligation. 
To test whether fatty acids really could be absorbed, oleic 
acid was fed in a paste with sugar. The animals were dissected 
at intervals and their crops preserved in Flemming’s fluid. 
Black globules of osmicated fat were readily found in the cells 
