PHYSIOLOGY OF DIGESTION IN BLATTIDAE SL. 
A general survey of the facts I have described about absorption 
leads to the conclusion that the process of digestion of fat in the 
crop follows the usual course: fat is acted upon in the lumen of 
the crop by a lipase which in all probability comes from the cells 
as a secretion. This splits it to fatty acid and glycerol in the 
ordinary way. The soluble products are absorbed and _ re- 
synthesized into fat by the cytoplasm of the epithelial cells and 
used by the body for its nourishment. As a first step in utiliza- 
tion, the fat passes from the cells to the blood plasma in the spaces 
behind the epithelium, and from here is carried to all parts of 
the body by the blood. 
There is absolutely no doubt that the presence of fat globules 
in the epithelium indicates that the cells have absorbed fatty 
material from the lumen. The globules are practically always 
present at appropriate intervals after fat is eaten, and appear 
uniformly throughout great regions of epithelium, giving the 
same pictures through whole sections and whole series of sec- 
tions in dozens of preparations. The globules may be seen in 
flat preparations and in transverse sections equally well, and 
may be demonstrated by staining with osmic acid, Sudan III, 
and Nile blue. Schliiter would have us believe that any fat in 
the cells had got there from the lumen directly through slits in 
the intima. This might occur occasionally; but an examination 
of my figures and my several lines of proof as given above, to- 
gether with the great uniformity of my preparations and their 
agreement with those of Petrunkevitch, makes it absolutely cer- 
tain that the cells of the crop absorb fatty matter in large 
amounts, and exhibit more and more of it in form of globules as 
digestion progresses. 
When a comparatively small amount of fat is eaten, it does not 
fill the lumen, but leaves part of the epithelium untouched. This 
untouched part shows no absorption stages, while the cells on 
which fat lies show fat within. Schliiter found the same condi- 
tion. This fact is additional evidence of the absorptive power 
of the crop; if the fat reached the crop by way of stomach and 
body cavity (as several authors contend it always does) it would 
surely appear fairly equally in all parts of the crop wall, and not 
merely in those regions which contain fat within. 
