DIGESTION OF PROTEIDS. 
599 
supposition is negatived by the rapidity of the action, and its progress 
in presence of antiseptics; and both by the recent observations of 
Miura, 1 which slimy that the mucous membrane of the intestine of 
newly-born animals, under antiseptic conditions, causes inversion. No 
inversion was obtained with the mucous membrane of the stomach or 
large intestine. 
Brown and Heron 2 have shown that the dried mucous membrane 
of the small intestine is much more powerful, both in its diastatic action 
on starch and in its inverting action on cane-sugar and maltose, than 
are infusions of the same material. Starch also disappears from an 
intestinal fistula (Thiry) much more rapidly than it is possible for the 
succus entericus, 3 judging from other experiments, to convert it into 
sugar. These facts point to a possibility that the epithelial cells of 
the intestinal mucous membrane may possess the power of absorbing 
starches and saccharoses, and submitting them to diastatic and inverting 
processes, in passing them on to the lymph spaces of the villi; that, in 
fact, cellular digestion of absorbed carbohydrates may take place hi the 
epithelial cells after absorption. 
The secretion of the small intestine is generally stated to be 
inactive towards lactose, so that the inversion of this sugar probably 
occurs after its absorption by the columnar cells. 1 
Human succus entericus has been investigated by Ewald, 5 by Deniant, 6 
and by Tubby and Manning ; " they all agree as to its diastatic action on starch 
and inverting action on cane-sugar. Tubby and Manning also tested its action 
on maltose, and found that this was converted into dextrose. The ferment or 
inverting material adhered to mucus whenever a precipitation of this took 
place in the fluid, so that the mucus was more effective than the clear 
fluid. 8 
DIGESTIOX OF PEOTEIDS. 
The digestion of proteids is a much more complex process than that of 
either the fats or carbohydrates, and one of which our knowledge is still 
less exact. In the digestion of carbohydrates we are absolutely certain 
that we have to do with a hydrolytic process, and that from a body 
of absolutely fixed percentage composition, though often of unknown 
molecular weight, there is produced in digestion a substance of known 
formula, and to a certain extent of km >wn structure. In proteid digestion, 
while it is probable that a very similar action is taking place, we have 
no such certainty. The digestive process begins with material, the 
different proteids, which varies considerably in percentage composition. 
1 Ztschr.f. Biol, Munchen, 1895, Bd. xxxii. S. 266. 
2 Proc. Boy. Soc. London, 1880, vol. xxx. p. 399. See also Shore and Tebb, Jour,). 
Physiol., Canil nidge and London, 1892, vol. xiii. {Proc. Physiol. Soc), and M. C. Tebb, ibid. 
vol. xv. p. 421. 
3 liohmann. Arch. f. d. ges. Physiol., Bonn, 18S7. Bd. xli. S. 424. 
4 Meyer, " Die Lehre von den chemischen Fermenten," 1882 ; Dastre, Arch, de physiol. 
norm, etpath., Paris, 1S90, tome xxii. p. 103 ; C. Voit and Lusk, Ztschr. f. Biol., Munchen, 
1891, Bd. xxviii. S. 275 : Mendel, Arch. f. d. ges. Physiol., Bonn, 1896, Bd. lxiii. S. 425. 
See, however, Pautz and Vogel, Ztschr.f. Biol., Munchen, 1895, Bd. xxxii. S. 304 ; Rohmaun 
u. Lappe, Ber. d. deutsch. chem. Gesel/sch., Berlin, 1895, Bd. xxviii. S. 2506. 
5 Virckow's Archiv, 1879, Bd. lxxv. S. 409. 6 Ibid., S. 490. 
7 Guy's Hosp. Rep., London, 1891, vol. xlviii. p. 271 ; Centralbl. f. d. med. Wissensch., 
Berlin, 1892, S. 945. 
8 Paschutin {loc. cit.) found that the inverting enzyme was mechanically precipitated 
along with collodion. 
