546 ME CHANISM OF SE CRE TION OF PAN C RE A TIC JUICE. 
beyond this. In another series of experiments the animals were fed 
with peptone (Chapoteaux). This, according to Chischin, was equivalent 
to reviewing the later stages of digestion, from the time when peptone 
began to be formed in any quantity in the stomach. The noticeable 
point about the results in these last cases is, that there is presented a 
great contrast to feeding with such a primary proteid as egg-albumin. 
With peptone, the juice becomes secreted in large quantities at once, 
its acidity is high, and its digestive power well marked. 
It is obvious, therefore, that the nature of the food has an important 
influence on the course and nature of the secretion. This has been 
drawn attention to by Khigine, 1 who classes the different foods 
mentioned above in different orders. He has also pointed out that the 
amount of juice secreted is not necessarily proportional to its acidity 
or its digestive power. These, again, are not necessarily proportional 
to each other, as is shown in the case of bread as food, when a low 
acidity in the secreted juice is shown, but a high degree of peptic 
power : whereas with milk a high degree of acidity is shown, but a much 
lower degree of digestive power. Finally, the duration of the digestive 
process is out of all relation to the strength of the secreted juice. It is 
impossible, then, to draw up any regular scheme of the course of digestion, 
except so far as specific foods are concerned, observations based upon the 
course of digestion of foods mixed in arbitrary proportions being of but 
little value. 
The Mechanism of Pancreatic Secretion. 
The histological appearances of the different secretory condi- 
tions of the pancreas. — The pancreas consists of secretory alveoli, 
between which are here and there seen masses of cells of a different 
character, and having no connection with the proper secretory channels 
of the gland. These masses of cells are presumably not connected with 
the ordinary processes of the secretion of a digestive juice, and the follow- 
ing account will therefore be confined to the typical secretory alveoli. 
If a small portion of the pancreas of an animal be examined in the 
living state, it will be found to consist of many secretory alveoli, and 
these secretory alveoli of cells contain numbers of discrete granules. 
It is generally found that whatever digestive stage the animal is in, there 
exists an outer zone in the alveolus free from granules. This is not, 
however, invariably the case. Ordinary stains, such as hematoxylin 
and carmine, are found to colour this outer zone more deeply than the 
rest. This is in conformity with the usual rule, that such stains do not 
deeply colour the secretory granules of cells, or the substance formed by 
their breaking down. If the cells are macerated for a few days in 
neutral ammonium chromate, a radial fibrillation is revealed 2 in this 
outer zone. The addition of water to the fresh gland causes the 
granules to disappear, ami dilute alkalies produce this result even more 
rapidly. Acids, either mineral or organic, cause the distinction between 
the two zones to be lost, the whole cell becoming clear. By hardening 
the gland in solutions of osmic acid, or in the vapour of osmic acid, the 
granules may be preserved. 
1 " Etudes sur l'exeitabilite seeretoive specifique de la muqueuse du canal digestif" 
Arch, de sc. biol., St. Petersbourg, 1895, vol. iii. p. 5. 
- Heidenhain, Hermann's "Handbueb," Bd. v. Abth. 4. 
