698 
MR, J. N. LANGLEY ON THE HISTOLOGY AND 
plasmic substance, i.e., of protoplasm and of the products of its metabolism which are 
kept imbedded in the cell; and that further in a great number of such cells the proto¬ 
plasmic and inter-protoplasmic portions are not optically distinguishable from one 
another in the living cells. Whether they are distinguishable or no depends mainly 
upon the refractive index of the inter-protoplasmic substance. The antecedent of 
pepsin in the above-mentioned gastric glands differs from the protoplasm sufficiently 
in refractive power to be visible in life. 
In the pyloric glands the inter-protoplasmic substance is almost altogether mucigen, 
having much the same refractive power as the protoplasm which formed it. It seems, 
then, not unnatural that the small amount of the antecedent of ferment contained by 
the pyloric gland-cells should be unable to render the inter-protoplasmic substance 
obvious in life. 
Since the pepsin of different animals differs somewhat in its properties,* it is pro¬ 
bable that both pepsin and its antecedent differ in different animals somewhat in 
chemical constitution. I can then readily imagine that the gastric gland-cells of some 
animals may form an inter-protoplasmic substance giving rise to a large quantity of 
pepsin, and yet having so nearly the same refractive index as the cell-protoplasm as to 
be very slightly or not at all visible without the action of reageuts. 
Since the inter-protoplasmic substance gives rise to pepsin, it is in the highest 
degree improbable that the cell should form pepsin in any other way than through 
the medium of the inter-protoplasmic substance. This means in the gastric glands we 
are considering, that pepsin is formed in the cells only through the medium of granules. 
If, then, two gastric glands secrete an equal amount of pepsin, they will have used up an 
equal, or, allowing for a slight difference in the chemical composition of the granules, a 
nearly equal, amount of granules. This deduction we shall have occasion to allude to 
later. 
During secretion the three chief phenomena which can he recognised in gland-cells, 
viz .:—(a.) a using up of granules, (b.)-a fresh formation of granules, (c.) a growth 
of protoplasm—go on simultaneously. The different aspects of the gland-cells 
depend upon the relative activity of these three processes. 
This view has been already put forward by Heidenhain to account for the changes 
which take place in the pancreas. He says :—t 
“ In the cells a continuous change takes place ; a using up of substance in the 
* See Hoppe-Seyler, Physiol. Chemie., s. 218, 1878. 
t “ An den Zellen findet ein forfcwahrender Wandel stafct; Stoffverbrancli innen, Stoffansatz aussen. 
Innen Umwandlung rier Kornchen in Secretbestandtheile, aussen Verwendung des Ernahrungsmaterials zur 
Bildung homogener Snbstanz, die sich. ihrerseits wiedernm in korniges Material umsetzt. Das Gesammtbild 
der Zelle liangt von der relative:! Geschwindigkeit ab, mit welcber sich diese Processe vollzieken. Die 
