104 SAPROPHYTISM, PARASITISM AND PATHOGENISM 
meconium, which is passed during the first eii2;hteen hours after birth, 
is sterile. Following this period of sterility there is a period lasting 
about three days on the average, in which various adventitious organ- 
isms are met with in the dejecta. The normal nursling flora begins 
to appear by the end of the third day, following the ingestion of 
breast milk. The dominant organism of this nursling flora is ordi- 
narily an obligate anaerobe, B. bifidus, which is one of the best known 
examples of obligately fermentative organisms. It does not thrive on 
a purely protein diet but requires carbohydrate as well, which is nor- 
mally supplied by the breast milk. Breast milk, it will be remembered, 
contains on the average about 7 per cent of lactose, 3 per cent fat and 
but 1.5 per cent protein. The proportion of carbohydrates to protein 
in the diet decreases as the infant becomes older and the diet becomes 
more liberal, and this decrease in the percentage of carbohydrate is 
associated with a diminution in the number of the obligately fermenta- 
tive bacteria, particularly of B. bifidus, and theu' gradual replacement 
by organisms which can thrive well on a diet containing variable pro- 
portions of carbohydrate and protein.^ 
B. coli is a most labile organism with respect to its ability to develop 
in the carbohydrate and protein constituents of the intestinal contents 
at the ileocecal region and lower levels; this organism is represented to 
the extent of fully 80 per cent in the feces of healthy men. Smaller 
numbers of other bacteria, as Micrococcus ovalis, B. acidophilus, B. 
proteus, B. mesentericus, B. aerogenes capsulatus and many other 
varieties are found transiently or semi-permanently in the intestinal 
contents. Hemolytic streptococci are uncommon in the intestinal 
tract^ and they are found only occasionally in the appendix. In a few 
cases, however, they may predominate in the latter, and then appear to 
be the principal etiological agent .^ Exogenic bacteria occasionally 
invade the tissues of the bod}^ through the intestinal mucosa. Thus 
typhoid, paratyphoid and dysentery bacilli and cholera vibrios may 
produce severe infections. The tubercle bacillus may pass through the 
apparently intact intestinal wall without leaving any evidence of its 
passage.'' It is supposed that this organism penetrates the intact 
mucosa and enters lymphatic channels suspended in the fats of the food 
and e^■entually proliferates in deeper tissues. 
3. Genito-urinary System. — Fa(/i?? a.— The vagina has an acid reac- 
tion and it harbors very few bacteria,^ but immediately after child- 
birth the reaction may become temporarily alkaline. The bacillus 
of Doderlein, however, occurs so commonly, that it may be provision- 
ally regarded as a normal inhabitant, and a few strains of aciduric 
cocci are not infrequently detected in cultures from the fundus of 
1 A more detailed discussion on intestinal bacteria and their significance will be 
found in Chapter XXIX. 
•' Davis: Jour. Am. Med. Assn., 1919, 72, 319. 
3 Kraft: Jour. Infec. Dis., 1921, 28, 122. 
* Bartel: Wien. klin. Wchnschr., 1904, 17, 414. 
'■' Demme and Baltzer: Arch. i. Gynakol., 1927, 129, 900 Demmo, Ibid., ]>, 91.3. 
