310 
A. H. LOGAN. 
and is with difficulty converted with grape sugar, and is 
called achroo-dextrin. The sugar thus formed is called 
ptyalose, which by the action of sulphuric acid is converted 
into grape sugar (glucose). 
Facts about ptyalin. (i.) The extremely small amount 
required to make the fluid effective. (2.) There is no ap¬ 
preciable diminution in the amount of the ferment, so it can¬ 
not be said to be used up in the process. (3.) It acts most 
readily in alkaline solutions; slowly in neutral, and not at 
all in acid the strength of two per cent, hydrochloric acid. 
(4.) Most active at bodily temperature. Excessive heat de¬ 
stroys it. Cold checks it. (5.) Strong acids or alkalies de¬ 
stroy its amylolytic power. (6.) It has but little effect on 
raw starch, its cellulose coating protecting it, but acts rapidly 
on well boiled starch. (7.) It is most active in weak starch 
solutions, and is much impeded in its action by an accumula¬ 
tion of sugar. 
To recapitulate we find the following changes take place 
in the mouth. (1.) Solid food is or should be finely sub¬ 
divided. (2.) Dry food is moistened. (3.) Rolled into a 
bolus. (4.) Subricated. (5.) The soluble part is dissolved. 
(6.) Part of the indiffusible starch is converted into soluble, 
diffusible sugar. 
The food is conveyed to the stomach by the act of deglu¬ 
tition, where it again undergoes changes by the action of the 
gastric juice. 
The gastric juice is a clear, colorless, strongly acid fluid, 
specific gravity 1,002. It is secreted by small glands situated 
in and below the mucous membrane of the stomach. There 
are two different kinds of cells lining the gastric glands and 
ducts, viz.: the spheroidal, which are most numerous, line the 
centre of the gland ; the others are oval in shape and are 
found on the parietal portions of the glands and in the ducts. 
The chief secretory activity of the glands resides in the 
central or spheroidal cells, and produces pepsin. Pepsin is 
also produced by the mucous glands at the pyloric end of 
the stomach. 
The formation of hydrochloric acid is not well understood, 
9 
