262 BACTERIOLOGICAL EXAMINATION OF MATERIAL 
symptomatology. The streptococcus is a common inhabitant of the 
intestinal tract, and for this reason streptococcus infection of the 
alimentary canal is denied by many observers. The streptococcus is 
frequently an important secondary invader of the intestinal mucosa 
in bacillary dysentery, and possibly in typhoid and paratyphoid 
infections as well. It is also frequently associated with an over- 
growth of the "gas bacillus" (B. aerogenes capsulatus) in intestinal 
infection with the latter organism. The occasional acute enteritis 
observed both sporadically and epidemically among \'oung children is 
also incited by streptococci. The distinction, if any exists, between 
the intestinal streptococcus and Streptococcus pyogenes is not clearly 
established. The isolation of streptococci from intestinal contents is 
made either by direct plating upon glucose agar, or by inoculation of 
feces into glucose broth. The streptococcus, as a general rule, produces 
enough acid in the medium after one or two days' growth at body 
temperature to seriously restrain the development of the intestinal 
bacteria. A Gram stain prepared from the sediment of the fermenta- 
tion tube will frequently reveal a nearly pure culture of the organism. 
A direct smear from the feces, stained by Gram's method, also will 
indicate the unusual preponderance of streptococci in acute Strepto- 
coccus enteritis. Blood-agar plates are also occasionally used in the 
isolation of streptococci from feces. 
The members of the alcaligenes, dysentery, typhoid, Morgan, paraty- 
phoid group— comprise the more important bacilli ordinarily sought 
for in the intestinal contents. Their isolation upon ordinary media is 
difficult because B. coli, the most important of the intestinal organisms, 
greatly outnumbers the more delicate pathogenic bacteria; its colonies 
on ordinary media are not readily distinguished from typhoid colonies. 
The modified Endo medium (see page 230), however, affords a ready 
means of identification between the pathogenic bacteria and B. coli. 
The Endo medium is essentially lactose agar containing a small 
amount of basic fuchsin decolorized with sodium sulphite. A better 
medium is lactose agar containing the Andrade indicator (see Media). 
Organic acids, including lactic acid, restore the color to fuchsin. None 
of the members of the alcaligenes-typhoid group ferment lactose, 
therefore, no lactic acid is formed in and around colonies of these bacilli. 
B. coli, on the other hand, ferments loctose, and consequently the 
colonies of this organism are colored red. The lactic acid resulting from 
the fermentation of the lactose locally restores the color to the fuchsin. 
Procedure.— K thin suspension in plain broth, prepared from a 
freshly passed specimen of feces, is incubated if possible for an hour 
at 37° C., then rubbed gently over the surface of an Endo plate with 
a sterile bent-glass rod or platinum needle. At the end of eighteen 
to twenty-four hours, small colorless transparent colonies are removed 
to 0.1 per cent glucose meat infusion broth for further development. 
Inasmuch as colonies of B. alcaligenes, dysenterise (Flexner, Shiga 
and other strains) typhosus, paratyphosus alpha and beta, and the 
