466 CHEMISTR Y OF THE DIGESTIVE PROCESSES. 
the later stages of putrefaction. It has also been suggested that the 
cause may be the absence of oxygen from the intestine, the ptomaine- 
forming bacteria being aerobic. That the bacteria which produce 
ptomaines are present in the intestine, is shown by the fact that cultures 
producing ptomaines may be obtained by sowing from the intestinal 
contents into suitable media. 1 At any rate, ptomaines even in traces are 
not to be found in the intestinal contents; and it is fairly certain that 
they are not produced there, as most of them, absorbed even in minute 
doses, are capable of producing profound toxic effects. 
The first stages in the action of bacteria on proteids are very similar 
to those induced by trypsin ; they can also be brought about by enzymes 
extracted from the bacteria, 2 but, according to Kiilme, 3 are not due to 
trypsin, which is never formed in bacterial putrefaction. 
The first action is the solution of the proteid, if this is not already 
dissolved. Solution takes place much more slowly than in the case of 
the digestive enzymes, the complete solution of fresh fibrin thoroughly 
infected with intestinal bacteria in faintly alkaline solution being a 
process of some days' duration. 4 Albumoses, peptones, and the other 
products of tryptic digestion are next formed, but the amount of these 
present at any time is never great, since they are gradually broken up 
as they are formed into more advanced degradation products. In the 
presence of albumoses or peptones, the native proteids are very faintly 
attacked by the bacteria, until these have first been disposed of. 
Neumeister 5 has shown that, when peptone is added to putrefying blood 
or proteid, its quantity is not increased by the continuance of the putre- 
factive process, but rather diminished until it finally disappears. 
The proteid molecule probably contains a large number of both 
fatty and aromatic radicles, but all those belonging to the aromatic 
group yield, under the action of trypsin, only one substance, namely, 
tyrosine. The same is true of all artificial modes of decomposition which 
do not act too intensely on the primary products of decomposition. 6 
But with the decomposition produced by bacteria, the case is different, 
and several aromatic compounds are formed. 
These are in part produced by further action on tyrosine, formed in 
an earlier stage, and in part spring from a specific action of the bacteria 
on the proteid, without the intervention of tyrosine. Only some of these 
products of bacterial decomposition have been hitherto found in the 
intestinal canal ; the others are either, under the different conditions, not 
formed there, or are so rapidly absorbed and altered that they cannot 
be detected in the intestinal contents. 
The chief aromatic compounds derived from the bacterial decomposi- 
tion of proteids are: — (a) Tyrosine, and its derivatives, paraoxyphenyl- 
propionic acid (hydroparacumaric acid), and paraoxyphenylacetic acid, 
as well as phenylpropionic and phenylacetic acids, 7 of which the fore- 
going are the oxy- or hydroxy-acids, also parakresol and phenol. 
1 Brieger, D utsche med. Wchnsehr., Leipzig, 18S7, S. 469; Baumann u. Udransky. 
Ztschr. f. p/iysiol. Chem., Strassburg, 18S9, Bd. xiii. S. 579. 
2 See p. 313. 
3 Dhtersuch. a. j. physiol. Inst, zu Heidelberg, 1878, Bd. i. S. 291. 
4 Bienstock, Ztschr. f. Hin. Med., Berlin, 1884, Bd. viii. S. 1. 
5 Ztschr./. Biol., Munchen, 1890, Bd. xxvii. S. 335; "Lehrbuch, " Th. 1, S. 207. 
6 Kiihne obtained indol by the fusion of proteid with caustic alkali, Bcr. d. dcutsch. 
chem. Gesellsch., Berlin, lS75,"Bd. viii. S. 206. 
7 See E. Salkowski, Ztschr./. physiol. Chen., Strassburg, 1SSJ5, Bd. ix. S. 491. 
