ABSORPTION OF PR O TEIDS. 44 r 
Neumeister ] states that albumoses and peptones dissolved in 
whipped blood car lie changed by mere contact with pieces of living 
intestine, the rapidity of change being increased when a slow stream of 
ah- is driven through the mixture, so as to bring the pieces of intestine 
into rapid contact with different portions of the blood and albumose. 
Hofmeister 2 observed a considerahle increase in the number of 
leucocytes in the intestinal wall during digestion of proteids, and argued 
from this that these took a considerable share in proteid absorption and 
in the conversion of albumoses and peptones in the adenoid tissue of 
the intestinal wall, and in the mesenteric lymphatics. There is little 
experimental ground for belief in such a theory. In the first place, 
proteid is not absorbed to any appreciable extent by the lymphatics; 
secondly, albumoses are not changed, as Hof meister 3 himself has shown, 
in the blood, which contains plenty of leucocytes; thirdly, Heidenhain 4 
has shown that the amount of leucocytes in the wall of the intestine 
(and the amount of active mitosis in these) is too small to render them 
adequate for such a purpose. Finally, Shore 5 has shown that, after 
slow injection of a small amount of peptone (-041) grms.) into a lym- 
phatic of the hind-limb in a dog, this can be detected again in the course 
of twenty minutes in the chyle flowing from a fistula of the thoracic 
duct, showing that it has traversed the lymphatic system unchanged. 
All these experiments go to prove that albumoses and peptones are 
modified during their passage through the epithelial cells by the action 
of living protoplasm. What substances are formed from them is not 
known by direct experiment, but it is highly probable that the process 
is one of conversion backwards into coagulable proteid. It is known 
that coagulable proteid can be artificially obtained from peptone and 
albumose, 6 and that albuniose and some forms of peptone used as foods 
can replace coagulable proteid in maintaining nitrogenous equilibrium. 
It is difficult to see how such a result can be attained otherwise than by 
a formation of coagulable proteid from albumose and peptone. 
The percentage of any proteid foodstuff, which is absorbed from the 
alimentary canal, may be deduced fairly accurately from a comparison 
of the amount of nitrogen in the food with that of the urine and faeces 
when such a food is taken into the system. 
Experiment shows that the various forms of proteid are utilised by 
the organism in widely varying degrees. It does not necessarily follow 
that a food of which the nitrogenous part is only partially absorbed is 
on that account to be despised as an adjunct to other classes of 
nitrogenous food ; vegetable proteid is absorbed much more imperfectly 
than that from animal sources; but vegetable food, amongst other 
things, is valuable for the consistency and bulk it gives to the food, 
^'Lehrbuch der physiol. Chem.," Jena, 1893, Th. 1, S. 251; Ztschr. f. Biol., 
Mlinehen. 1S90, Bd. xxvii. S. 324. 
2 Arch. f. exper. Path. u. Pharmakol., 1885, Bd. xix. S. 32 ; 1886, Bd. xx. S. 291 ; 
18S7, Bd. xxii. S. 306. See also Pohl, ibid., 18S8, Bd. xxv. S. 31 ; Heidenhain, Arch. f. 
d. ges. Physiol., Bonn, 1888. Supp. Heft., Bd. xliii. S. 72. 
3 Hofmeister (loc. tit., Bd. xix.) is of the opinion that the portion of "peptone" which 
lie believes enters the blood unchanged is converted in the tissue, "peptone" being found 
during digestion in the arteries but not in the veins. The presence of any albuniose or 
peptone, even in the arteries, is, according to more recent observers, however, very doubt- 
ful. 
4 Loc. cit. 
5 Journ. Physiol., Cambridge and London, 1890, vol. xi. p. 553. 
6 See p. 400. 
