5 5 4 ME CHAN ISM OF SE CRE TION OF INTESTINAL JUICE. 
It has been pointed out by Mette that during normal digestion there is a 
certain independence between the secretion of ferment and the secretion of water. 
Observations have also been made by Wassilieff 1 on the influence of food in 
causing changes in the activity of the juice. He found that the maximum of 
secretion was in the first two hours, with meat diet in the first hour, and 
milk diet in the second hour. By changing the diet from meat to bread and 
milk, the proteolytic action of the juice diminished, whilst the diastatic action 
remained unaltered. On the other hand, when changing from bread and 
milk to meat, these were reversed. It is therefore to be noted that the 
relative quantity of both ferments is variable and dependent upon the food. 
The effects produced by other substances upon the flow of pancreatic juice 
have already been mentioned (p. 551). 
The Mechanism of Secretion of Succus Entericus. 
The histological evidence of secretion in the intestine.— The 
evidence of secretion from the histological standpoint is, in the case of 
the mucous membrane of the intestine, very incomplete. Paneth 2 pointed 
out that the cells at the base of the crypts of Lieberkiihn frequently 
contain definite granules. These cells were also studied by Nicolas, 3 
who noticed different phases in the condition of the cells; thus, after 
secretory activity, ho found them either free from or containing but 
few granules. 
Hardy and Wesbrook 4 found that in fasting animals the granules 
were large and numerous, in well-fed animals comparatively few, and 
smaller than in the fasting state. 
Bizzozero 5 regards the granules as mueigen granules. Sehaffer ° 
has also called attention to the fact that the cells containing them 
are goblet - shaped. From the manner in which they stain, their 
shape, and the fact that they are scattered in the crypt of Lieberkuhn, 
it seems probable that they are to be looked upon as mucus-secreting 
cells. 
The cells covering the villi have been described by Nicolas 7 as con- 
taining granules which do not stain, or at the best very slightly, with 
safranin (unlike those just referred to). He states, however, that these 
granules give rise to some secretion. Examined in the fresh state, 
the cells do not show the existence of typical secretory granules. 
Brunner's glands, from their structure, suggest the formation of 
a mucous secretion, 8 but it has been stated by Krolow 9 that an extract 
of the glands will digest fibrin in acid solution, and they bear 
considerable resemblance, histologically, to the pyloric glands of the 
stomach. 
The experimental evidence of secretion of succus entericus. — 
Two methods have been adopted for obtaining evidence as to the 
nature of succus entericus. The first consists in isolating, by operation, 
a piece of the intestine, and observing the nature of the liquid which 
1 Arch, de sc. biol., St. Petersbourg, 1893, vol. ii. 
- Arch./, mikr. A not.. Bonn, 1S8S, Bd. xxxi. 
:: Interned. Monatschr. f. Anat. u. Physiol., Leipzig, 1S91. Bd. viii. 
4 Journ. Physiol., Cambridge and London, 1S95, vol. xviii. 
5 Anat. Anz., Jena, 1888, Bd. iii. ; Atti d. r. Acad. d. sc. di Torino, 1888-9. 
,; Sitzungsb. d. k. Akad. d. Wissensch., Wien, 1891, Abth. 3, Bd. c. 
7 Op. cit. 
s Kuczynski, Interned. Monatschr. f. Aunt. u. Physiol., Leipzig, 1890, Bd. vii. 
;| Berl.klin. Wchnschr., 1870, No. 1. 
