1884.1 
Intestinal Mucous Membrane. 
281 
Turbellaria display this intercellular digestion. There are 
some whose intestinal cells have completely lost the power 
of taking up nourishment, — a fadt which is also recognised 
in the Rotatoria, the Annelides, and many other worms. 
As in the remaining evertebrates — e.g., in the arthropods 
and the mollusks — nothing has been as yet ascertained 
concerning intercellular digestion, we might incline to the 
assumption that the above-mentioned pristine method of 
taking up nourishment has not been inherited beyond the 
worms, and that the intestinal epithelium has lost its 
amoeboid character, and has become to a certain degree 
consolidated along its free margin. We might be disposed 
to view the strongly refringent basal border, recognisable in 
the intestinal epithelium of most mammals, as such a 
solidified outer zone. As regards its more intimate struc- 
ture various views have been suggested, which, however, by 
no means fully explain the reception of nourishment as it 
occurs in the intestine. On this subject the following fadts 
are known : — 
The molecules of fatty matter can be traced diredtly on 
this passage through the body of the cells. As regards the 
reception of the albumen we had no definite ground for 
asserting an adtive participation of the cellular protoplasm 
as it takes place in the above-mentioned evertebrate ani- 
mals. It was therefore assumed that albumen was taken 
up by means of processes of diffusion and filtration. Al- 
though the diffusive power of soluble albumen is too low to 
explain its necessary abundant transmission into the blood, 
yet the peptones possess a diffusive power fully sufficient to 
meet the necessities of the case. 
As regards the mucous membrane of fishes and amphi- 
bians, Dr. R. Wiedersheim (“ Naturforsch. Gesellschaft zu 
Freiberg,” and “ Naturforscher ”) has observed certain fadts 
which are not unimportant in their bearing on this 
question. The intestinal canal of those vertebrates which 
are regarded as phyletically the oldest — the Amphioxus and 
the Cyclostomi — are completely devoid of pepsine glands, 
and here, consequently, the formation of peptones is entirely 
out of the question. The question therefore arises whether 
here, where a stomach is entirely excluded, there exist in 
the intestinal mucous membrane arrangements which — in 
contradistinction to what holds good in the higher verte- 
brates — permit the absorption of unmodified albumen. The 
following fadts, observed by Dr. Wiedersheim, may pave the 
way to a diredt reply to this question. 
VOL. VI. (THIRD series.) 
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