LEO F. RETTGER 647 



the administration of i gm. of lactose or dextrin plus i cc. of fresh broth culture 

 daily to white rats, and 150 gm. of lactose plus 150 cc. of broth culture to man. It 

 appeared from their experiments also that implantation may be brought about with 

 2 cc. of broth culture alone in the rat and with 300 cc. in man. 



Perhaps the most far-reaching and practical observations of these authors were 

 those made on milk cultures of L. acidophilus. In some instances 500 cc. of a twenty- 

 four-hour acidophilus-milk culture were sufficient to bring about simplification of 

 the flora in man, and the use of 1,000 cc. taken daily in two or three portions, or of 

 500 cc. of the milk and 100 gm. of lactose, proved to be effective in establishing a flora 

 composed largely of L. acidophilus. Since L. acidophilus assumes such prominence in 

 the intestine of normal children subsisting on milk, and since it may be implanted 

 and induced by appropriate diet to grow and establish itself in human subjects of all 

 ages, it has been employed in numerous investigations with persons suffering directly 

 or indirectly from intestinal disturbances (Rettger and Cheplin;' Cheplin, Post, and 

 Wiseman;^ Reddish;^ Kopeloft";^ and others), and as a result of these investigations 

 is today widely used as a therapeutic agent, particularly in the form of milk culture 

 or what is generally known as "acidophilus milk." 



After several years of intensive effort to produce pure, viable, commercial acid- 

 ophilus milk under strict laboratory supervision, this product has been made available 

 throughout a large part of the country and is now occupying an important place as a 

 health drink as well as a therapeutic agent among the so-called "cultured milks." 



It seems to be quite well established that the viability of the organism is preserved 

 better and for longer periods of time in milk than in other known media. Milk prop- 

 erly ripened with selected strains of L. acidophilus has a smooth creamy consistency 

 and a characteristically agreeable odor and flavor. The curd is extremely fine and 

 easily tolerated, and there is little wheying off at best. 



Special methods for determining the viability of acidophilus products have been 

 devised. One of these, which has attained very wide usage and has virtually assumed 

 the role of a standard method, involves the use of whey agar (Rettger and Cheplin)" 

 and the application of from 5 to 10 per cent of carbon dioxide gas to the plates in 

 closed containers (Kulp).*^ 



Different strains of L. acidophilus from one and the same, and from different 

 sources, vary among themselves, though they are bound together by group character- 

 istics, and may readily be distinguished from L. bulgaricus in certain important re- 

 spects; chief among these are a difference in deportment toward maltose (Rahe' and 

 Kulp^), a difference in the degree of acid production in definite periods of time, and 

 in the ability to establish themselves in the intestine. 



L. acidophilus may be distinguished also from L. bijidus and L. odontolyticus- 



' Rettger, L. F., and Cheplin, H. A.: Arch. Inst. Med., 29, 357. igzi 



' Cheplin, H. A., Post, C. D., and Wiseman, J. R.: Boston M . 6° S. J ., 189, 405. 1923. 



■5 Reddish, G. F.: Virginia M. Monthly, 50, 409. 1923. 



'' Kopeloff, N.: Lactobacillus acidophilus. Baltimore, 1926. 



s Rettger, L. F., and Cheplin, H. A.: Intestinal Flora. New Haven: Yale University Press, 1921. 



' Kulp, W. L.: Science, 64, 304. 1926. 



'Rahe, A. H.: J . Infect. Dis., 15, 141. 1914. * Kulp, W. L.: J. Bact., g, 357. 1924. 



