436 The Submaxillary Gland 
alveolus, one notes the formation of mucous globules within the cells 
which stain a deep blue 
with one of the elements of 
the Mallory stain. The mu- 
cous globules appear to be 
formed in the part of the 
cell next to the lumen, as 
the nucleus is pushed off to 
the edge nearest the base- 
ment membrane where it 
begins to show some signs of 
intracellular pressure, evi- 
denced by its semilunar 
form. At the same time the 
nucleus takes a red stain, 
while the nuclei of the pari- 
etal cells remain brown in 
color. 
Fria. 11. Terminal cluster of alveoli from the sub- / : : 
maxillary gland of pig’s embryo 12 centimeters long. At this time the mucous 
Hardened in Zenker’s fluid and stained by Mallory’s ll f 
method. xX 650 dameters. The definite arrange- cells are not much larger 
Auaoatis Miicoue colle toumed from the couteal. , thane thosep of, the auemiemt 
EE eeu aoparent. Alveolar ampullae are also group an de ther cytoplasm 
looks like a reticulum of 
even blue lines or else as a mass of minute globules closely pressed to- 
gether within the limits of the cell. At a somewhat later stage (Fig. 
11) the arrangement of the cells is more definite and they are placed 
in two distinct layers. Mucous cells have increased in size but other- 
wise show the same characteristics of the cells at an earlier period. In 
an alveolns of a pig 18 centimeters long (Fig. 12) the mucous cells 
have begun to approximate laterally and, in some instances, have 
reached and impinged upon the reticulated membrana propria of the 
alveolus. The parietal celis now show evidences of pressure and are 
grouped off towards the reticulated membrane between adjacent mucous 
cells. In these instances, however, the parietal cells are not as a rule 
single, but occur in clumps of three or four. In many places the 
mucous cells. are still separated from the basement membrane by an 
entire layer of parietal cells. 
The alveoli in a pig two days old (Fig. 13) show, in general, a con- 
siderable advance in the arrangement of the mucous cells.. They be- 
come larger and, as a rule, either rest upon the basement membrane or 
are separated from it by a very slight distance. The distended mucous 
