MATERIAL FROM THE LIVING SUBJECT 261 
A sterile catheter must be used, aud the first portion of the urine should 
be discarded. Under ordinary conditions, except in tubercle infections, 
the causative organisms will be present in suflficient numbers so that a 
direct smear of the sediment, stained by Gram's method, will furnish 
a valuable clue to the method and media to be used for the isolation 
and identification of the organism. 
Blood agar is a favorable medium for the isolation of the strepto- 
coccus, pneumococcus, gonococcus and staphylococcus. The gono- 
coccus is usually recognized by a Gram-stained smear without further 
attempt at isolation. It is a Gram-negative diplococcus wdiich, in 
acute infection, usually appears both intra- and extracellularly among 
polymorphonuclear leukocytes. Micrococcus catarrhalis, which might 
easily be confused with the gonococcus in its morphology, occurs 
very rarely in genito-urinary infections; ordinarily it may be disre- 
garded. Micrococcus (Bacillus) melitensis grows very slowly upon 
ordinary media. Its very small size together with the deliberateness of 
growth usually suffice to attract attention to its presence. An agglu- 
tination with a specific serum completes the diagnosis of Malta fever. 
Streptococci and pneumococci produce distinctive changes in the hemo- 
globin of blood-agar plates. Their final identification is discussed in the 
section devoted to these organisms. B. coli and B. proteus are common 
incitants of cystitis; they grow readily upon ordinary media and their 
recognition depends upon the changes pure cultures induce in artificial 
media. (See table, page 353.) 
B. typhosus and members of the paratyphoid group are occasionally 
found in the urine of patients and convalescents. The organisms are 
readily obtained in pure culture by plating upon nutrient agar, or, 
better, upon the modified Endo medium with the Andrade indicator 
(see page 230). Their cultural characteristics and agglutination with 
specific sera establish their identity. Tubercle bacilli may be found 
in the urine; the only satisfactory and trustworthy diagnosis is made by 
injecting the sediment of a twenty-four-hour sample of urine subcu- 
taneously into a guinea-pig. The animal will succumb to infection if 
tubercle bacilli are present, but will fail to react to smegma bacilli, 
which are acid-fast and resemble tubercle bacilli morphologically. 
Examination of Feces. — (See also Special Section, Bacteriology of 
the Feces).— The isolation and identification of pathogenic micro- 
organisms from the feces is frequently a difficult task, because the 
normal intestinal bacteria preponderate, even in severe infections. 
Nevertheless, the use of special media has greatly reduced the diffi- 
culties, and a search for specific microorganisms is now possible with 
a very favorable outlook for success. 
For convenience, intestinal infections may be divided into those 
caused by cocci, by bacilli, and spiral organisms. Of the spherical 
organisms or cocci, the streptococcus is by far the most common 
pathogenic organism encountered in intestinal infections, although 
an overgrowth of Micrococcus ovalis may be associated with distmct 
