76 
consisting of two parts: the Foot, attached 
to the Tunica propria, narrow, protoplasmic 
and containing the nucleus ; and the Theca, 
opening into the lumen of the intestine, broad 
and filled with a secretion termed mucus. 
The protoplasm of the goblet cells is much 
denser in texture than that of the cylinder 
cells, and their nuclei stain more intensely. 
Two of these cells never occur in juxtaposi- 
tion, cylinder cells being always inter- 
posed. 
Closely associated with these two ele- 
ments, although having only a topograph- 
ical relation with them, are Leucocytes or 
wandering cells. These occur in various 
positions within the mucus membrane, 
either between or beneath the epithelium 
cells. In the former position they usually 
lie in a line with the nuclear row; rather 
less frequently nearer the lumen of the in- 
testine. In the latter position they are 
scattered throughout the connective tissue 
stroma, and may, in the higher vertebrates, 
form dense aggregations, termed nodules. 
A nodule consists of a connective tissue 
frame-work, inclosed by a delicate mem- 
brane, the whole closely packed with leu- 
cocytes. The nodules may occur singly or 
in groups, in which latter case they consti- 
tute follicles. Peyer’s patches are a famil- 
iar example of these structures. Their ac- 
tual position is within the mucosa, but they 
encroach, on one side, upon the submucosa, 
and, on the other, may break through the 
mucus membrane and project into the cav- 
ity of the intestine. 
The three elements above described make 
up, in its entirety, the lining of the verte- 
_ brate intestine, and it is through them and 
by their means that food, after being acted 
upon by digestive fluids, is absorbed and 
eventually distributed throughout the vari- 
ous parts of the body. Three phases may 
then be distinguished in digestion: First, 
the sifting-out of the useful constituents of 
the food from the useless and the reduction 
SCIENCE. 
[N.S. Von. X. No. 238. 
of the former to a condition in which they 
may pass through the intestinal mucus 
membrane. Concerning these processes a 
considerable fund of accurate information 
has been collected. There is much differ- 
ence in detail in different groups of ani- 
mals; but in general, nitrogenous bodies 
are transformed into peptone, carbohy- 
drates into mono-saccharides, while fats 
are apparently broken up into a soap and 
glycerine. The change in the nitrogenous 
bodies is brought about by pepsin and tryp- 
sin. Carbohydrates are acted upon by 
ptyalin and amylopsin. Concerning fats 
the customary statement is that they are 
first emulsified by bile and then analyzed 
by steapsin. It is noteworthy that the 
pancreas furnishes enzymes capable of di- 
gesting all classes of food. The above doc- 
trine is that generally accepted, and, beyond 
any doubt, it is entirely correct so far as it 
goes. But there are reasons for believing 
that the cylinder cells of the intestine are 
also of great importance in the furnishing 
of digestive fluids. Howell (American 
Text-book of Physiology, 1896), speaking of 
“succus entericus,’ says: ‘‘ Upon proteids 
and fat it is said to have no specific action. 
* > Upon carbohydrates the secretion has 
an important action.”’ Foster (A Text-book 
of Physiology, Philadelphia, 1895) also 
mentions the succus entericus, but ascribes 
very little importance to it. On the other 
hand, Landois (Lehrbuch der Physiologie 
des Menschen, 9 aufl., 1896) summarizes the 
action of intestinal juice (Darmsaft) as 
follows : 
1. Diastatic action. 
2. Metamorphosis of maltose into glucose. 
3. Conversion of fibrin, fresh casein, 
raw and cooked meat and plant albumin 
into peptone. 
4. Analysis of fat. 
5. Metamorphosis of di- into mono-sac- 
charides. 
6. Coagulation of milk. 
