I. HISTORICAL REVIEW 



Thk present studies mark a resumption of work begun in this labora- 

 tory eight years ago. The new data recorded here are the results of 

 investigation into phases of intestinal bacteriology which are as yet 

 comparatively new and the importance of which is attested by the 

 almost universal interest which is manifested in them by physicians and 

 laymen alike. 



While it is a well-established fact that diet exercises a most profound 

 influence in determining the predominance of one or another type of 

 bacteria in the alimentary canal, the question of transforming and 

 simplifying the ordinary mixed intestinal flora through diet in con- 

 junction with the oral administration of bacteria, or by the latter 

 process alone, is still in its incipiency. 



The first systematic study of intestinal bacteria appears to have been 

 carried out by Escherich (1886) who made an extensive investigation 

 of the microorganisms in infants' dejecta, both in health and disease. 

 He observed the great predominance of Gram-positive rods in the stools 

 of healthy nurselings, but failed to isolate two organisms to which con- 

 siderable interest is attached at the present time, namely B. bifidus and 

 B. acidophilus. Through the classical researches of Tissier (1900) 

 and Moro (1900a) these two organisms were added to the list of known 

 intestinal bacteria. The controversy as to whether Tissier's B. bifidus 

 or Moro's B. acidophilus is the predominating type in the normal 

 dejecta of breast-fed babies was ended by the admission by Moro of 

 Tissier's claim (1900b and 1905a), which was substantiated by Ro- 

 della (1901), Cahn (1901), Cippolina (1902), Passini (1903), Weiss 

 (1904), and finally by Jacobson (1908). 



By means of a dextrose broth medium containing 0.5 per cent glacial 

 acetic acid, as first suggested by Heymann (1900), Finkelstein (1900), 

 working independently, isolated an organism identical with that of 

 Moro, which he called "Saureliebender Bacillus." 



The meconium of the new-born infant is sterile. Billroth (1874) is 

 given the credit by Mannaberg (1898) of having first observed this 

 fact. Senator (1880) found the intestine to be free from bacteria, and 

 his statement was confirmed by Escherich (1885), Popoff (1892), 

 Schild (1895), Szego (1897), Tissier (1900) and Moro (1900a). 

 While Breslau (1866) has shown that the early infection of the meco- 

 nium may be entirely independent of feeding, the mouth and the anus 



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