392 ELDON W. SANFORD 
lular endings of tracheae in the cells of various tissues; these 
tracheae are said to branch in the plasma of the cells, some 
of the brachlets passing into adjacent cells. I have never been 
able to find any such striking appearances in my preparations. 
Petrunkevitch described the end cells of the tracheae, and fig- 
ured the two types which occur; one type forms an integral part 
of the epithelium of the crop and resembles the other cells ex- 
cept for its narrowness and the tracheal connection below; the 
other type lies immediately below the ordinary epithelial cells 
and does not extend to the intima (fig. 2). Within each type of 
cell may be found the minute ending of the lumen of a tracheal 
branchlet. The tracheal tubes are bounded throughout by peri- 
tracheal cells, in which nuclei are always visible, but whose cell 
boundaries are not defined. 
Petrunkevitch has also described four very interesting appear- 
ances which occurred in preparations made at intervals after fat 
had been fed. These four phenomena are: 1) the presence of 
many tiny globules of osmicated fat in those tracheal end cells 
which form an integral part of the epithelium, the globules being 
identical with those of the ordinary cells, and evidently repre- 
senting fat absorbed from the lumen; 2) fat in the tracheal 
tubes, usually lying along the inner walls of the tubes and upon 
the coils of the spiral, supporting structures, and even moving 
along the spirals or moving out into the lumen to lie in a sticky - 
deposit there; 3) the presence of globules of osmicated fat in the 
peritracheal cells; 4) the presence in the lumen of certain tubes 
of a sticky deposit which resembled the contents of the crop’s 
lumen, and which sometimes contained leucocytes and fat glob- 
ules. These four appearances were described as representing 
four stages in one process which occurred as follows: The fat is 
absorbed by the tracheal end cells and passes. from their cyto- 
plasm into the minute terminal lumina of the tracheal tubes. 
In these the fat tends to lie on the spirals, and to proceed along 
the tubes in a spiral course by slipping along the spirals. It is 
now absorbed by the peritracheal cells and utilized by them. 
Not only fats are passed into the. tracheal tubes through the 
tracheal end cells, but also other foods, and these appear as a 
