HISTOL O GICA L C 1IAR. 1 CI 'ERS. 
The following table is taken from Colin: 1 — 
477 
Weight in Grammes of — > 
Parotid. 
Submaxillary. 
Sublingual. 
Horse .... 
Ox 
Sheep .... 
400 
283 
43 
86 
298 
36 
23 
43 
4 
Some Histological Characters of the Salivary Glands. 
It would be outside the scope of this account to give a detailed 
description of the ducts, ductules, terminal tubes, lymphatics, and other 
histological features of the several glands. But some of the histological 
features have so intimate a relation to physiological observations, that it 
is not advisable to pass them by without notice. 
The narrow ductule, proceeding from a duct, commonly divides, and 
each secondary ductule widens more or less suddenly into a tube of 
secreting cells; each tube gives off curved branches, and these also may 
give off similar branches ; thus, a clump of tubes is formed around the 
primary ductule. The terminal tubes are usually called alveoli, and their 
cells alveolar cells. 
The alveolar cells may be classified according to the chemical nature 
of the substances they secrete. A step in this direction was taken by 
Heidenhain, who divided the cells into mucous cells which secrete mucin, 
and albuminous cells which secrete some form of proteid. There is good 
evidence that the typical albuminous cell does not secrete any mucin, 
and there is some evidence that the typical mucous cell does not secrete 
any proteid, and on this basis it is apt to be assumed that all the alveolar 
cells secrete either mucin only, or proteid only. It should, however, be 
remembered that this is an assumption ; it is possible that some alveolar 
cells secrete both mucin and proteid. 
In any one salivary gland all the alveolar cells may be mucous or 
all may be albuminous, or some of them may be mucous and some 
albuminous. Further, in different glands, the relative number of the 
two kinds of cells varies in nearly all possible proportions. The 
nomenclature in use takes notice of the broad distinctions only. Glands 
which consist almost entirely of albuminous cells are called albuminous 
glands, those which consist chiefly of mucous cells are called mucous 
glands. The glands of intermediate structure are commonly placed 
in the class of mucous glands, unless the proportion of mucous to 
albuminous cells is very small. 
The term "mixed gland" was introduced for certain special cases; for example, 
the submaxillary gland of the guinea-pig, in which one or more lobules were 
said to be mucous and the rest to be albuminous. But in the guinea-pig, and 
possibly in the other cases, the mucous lobule appears to be a separate gland 
(cf. above, p. 476). It would probably be more convenient to use the term 
" mixed," for a gland in which the mucous and albuminous cells are present 
in approximately equal proportions. And we might have the following scale, 
passing from entirely albuminous to entirely mucous : — albuminous glands, 
1 "Traite de physiol. cornparee des auiraaux, " 3rd edition, 1886, tome i. 
