THE GASTRO-INTESTINAL FLORA OF NORMAL INFANTS 587 



The duodenum of adults is relatively poorly populated with bac- 

 teria in interdigestive periods, and Gushing and Livingston 1 have 

 called attention to the relative innocuousness of gunshot wounds at 

 this level as contrasted with those at lower levels, where peritonitis 

 practically invariably follows perforation of the gut. This phenomenon 

 is not wholly attributable to the comparative paucity of bacteria in 

 the duodenum as contrasted to lower levels; a final explanation is 

 lacking at the present time. According to Gessner, 2 staphylococci 

 and streptococci are numerous in the duodenum, and Tavel and Lanz 3 

 have made similar observations. Recently Hess, using a duodenal 

 catheter, 4 has studied the duodenal flora in normal individuals. He 

 finds the bacterial content very low in interdigestive periods; staphy- 

 lococci and a few Gram-positive and Gram-negative bacteria were 

 the prevailing types. These Gram-negative bacteria were not Bacillus 

 coli. Breast-fed infants showed fewer bacteria in the duodenal region 

 than did bottle-fed babies. 



The lower levels of the small intestines become progressively richer 

 in bacteria. The relative slowness with which food passes through 

 the intestines at the lower levels probably is a potent factor in creating 

 conditions favorable for continual bacterial growth. As a rule cocci 

 still predominate in the lower jejunum and upper ileum, but Gram- 

 negative bacilli of the colon group appear in moderate numbers. 



The cecum and ascending colon are the regions of most intense bac- 

 terial proliferation in health, but the number of living bacteria in the 

 intestinal contents diminishes rather abruptly from the sigmoid to the 

 rectum. It has been stated that at least 90 per cent, of the bacteria 

 of the feces are dead, or so attenuated in vitality that they are 

 incapable of growing in artificial media. For various reasons the 

 accuracy of this statement may be questioned, but there is little doubt 

 that the numbers of viable bacteria in the relatively desiccated feces 

 are less than those in the more fluid intestinal contents at the level 

 of the cecum. 



The bacteria commonly present in the ileocecal region are undoubt- 

 edly of many and varied types, but in general aerogenic bacilli of the 

 colon type 5 (including probably members of the proteus group as well) 



1 Contributions to the Science of Medicine by the pupils of William Welch, 1900, 543. 



2 Arch. f. Hyg., 1889, ix, 128. 3 Mitt. a. klin. d. Schweiz, i. 



4 Ergebnisse der inn. Med. u. Kinderheilk., 1914, xiii, 530. 



5 Ford, Classification and Distribution of the Intestinal Bacteria in Man, Studies from 

 the Royal Victoria Hospital, 1903, i, No. 5; MacConkey, Jour. Hyg., 1905, v, 333, 

 have described the common types of aerobic bacilli in the intestinal tract. The cultural 

 characters of the various aerogenic lactose-fermenting organisms, grouped for con- 

 venience as the colon group, are clearly set forth in these monographs. 



