THE INTESTINAL FLORA OF THE INFANT UNDER PHYSIOLOGICAL CONDITIONS The intestinal content. in the newborn child are free from germs; but infection of the intestine follows very quickly (within four to ten hours after birth), so that we can demonstrate microscopically bacteria in the second or third evacuation of meconium. The preparations of meconium show a very characteristic picture, peculiar to this time of life iPlate 53, Fig. I). The meconium flora are distinguished by mani foldness of form, but comparatively small number; as well as by the constant occurrence of hacteria containing spores. Of the latter, we especially note rods that take the stain poorly, carrying at one end an oval, staining spore. These have been called by Eseherieh "little head" bacteria; and their narrow form has been compared to that of spermatozoa. Besides these, we find, usually, plentiful cylindrical rods, containing large ,pores. In some preparations, the spore-bearing bacteria predominate; in others, long, rather thick, partly stained bacteria, at times some of them wave-like and slightly bifid at the ends, are in the foreground. Their appearance precedes that of the spore-bearing bacteria. We must emphasize, besides this. the frequent presence of different kinds of cocci; and the regular presence of oval, short rods, not taking Gram's stain.
When the child is put to the breast and the first milk-stool appears, the vegetation alters suddenly-. The previous flora make place for new varieties. We find thin rods predominating, usually pointed at both ends, which stain with Gram's method. These have a tendency to group themselves as diplobacilli, and sometimes show definite branchings. These bacteria multiply very- rapidly and completely predominate in the field of the microscope (Plate 53, Fig. VI). I have proposed the name of the physiological fecal flora of infancy for this distinct type of flora in the stools of the breast-fed infant.
So long as the child is at the breast, and is healthy, the character of the picture does not change. With the introduction of artificial nourishment, a typical change of flora appears, however. The one type of vegetation soon entirely di.appears, and in its place we have the picture of fecal flora of the child fed on cow's milk (Plate 53, Fig. II), which, in contrast to the previous picture, is characterized by a great multiplicity of species and their polymorphous character, as well as by the predominance of bacteria negative to Gram's stain. The follow ing laws may be deduced from these microscopic findings: 1. The intetinal flora depend upon the kind of food taken by the infant. If the newborn child is fed from the beginning with cow's milk
or in any other artificial w-ay, it will never have the physiological flora in its intestine; but if an artificially-nourished child has human milk given it at a later period, the physiological flora will appear in the feces after two or three. days, with absolute regularity. The knowledge of this interesting fact gives the investigator the opportunity to decide, from a study of the feces alone, whether the child is nourished naturally or artificially.
2. The microscopic picture of physiological intestinal flora is uni form and constant. —The oceasionally encountered eoeci and bacteria negative to Grain's method in the stool of the nursing infant are present in such a small number that they can never, under normal conditions, influence the uniform picture of the flora. The results of culture are, to a certain extent, in conflict with the results obtained by microscopic investigation; for instance, the more sensitive method by culture shows us a iarger munber of types than we can expect to find by the microscopic method, and shows that thc greater number of bacilli in the stool of the nursing infant are identical with the bacillus bifidus communis (Tissier). The bifidus is a strictly, anaerobic bacterium, and is most easily cultivated on glycerin-sugar-agar. The most marked characteristic of its many morphologically interesting variations in growth on culture-media is the formation of ramifications resembling the antlers of a deer (Plate 53, Fig. IX). Besides this chief representative of the physiological fecal flora, Tissier obtained regularly from the stools of nursing infants three other types; the bacillus coli cornmunis, the bacillus lactis iMrogenes, and the streptococcus Tfirsh-Libmann. To these I have lately been able to acid three obligatory intestinal bacteria of nursing infants: the bacillus achlophilus, the "little-head" bacter ium, and the motionless butyric-acid bacillus—the latter confirming Passini's findings. The motile butyric-acid bacillus and the putrefaetive bacillus putrificus coli Bienstock (both markedly anaerobic) are also frequently, but not constantly, present in the stools of nursing infants. Altogether, I have been able to isolate nineteen different varieties from the stools of healthy nursing infants. In spite of this relatively large number, I am conscious of the fact that I have by no means exhausted the number of bacteria inhabiting the intestines of the breast-f ed inf ant.