FATS AS ESSENTIAL DIETARY COMPONENTS 871 



affects the reaction. For example, ludder and Dewey^'^ found that 

 propionate had a shght stimulatory effect upon the growth of the ciliate 

 Tctrahymena geleii in low concentration, but was inhibitory at higher 

 concentrations, Avhile butyrate was ne\'er stimulatory at any concentration, 

 and rapidly became inhi])itory. Laurie acid also inhibited growth, as 

 did all the higher fatty acids tested (oleic, linoleic, linolenic, arachidonic, 

 vaccenic), and a Csn unsaturated fatty acid. Concentrations as low as 

 30 to 70 )Ug./ml. were sufficient to suppress groAvth completely. 



Trager^^" studied chickens and ducks experimentally infected with 

 a^'ian malaria {Plasmodium lophurae and P. cathemerium) . When P. 

 lophurae was cultured in vitro in suspensions of duck erythrocytes, plasma 

 protein fractions rich in a fat-soluble factor resembling biotin inhibited 

 multiplication, while comparable concentrations of plasma fractions poor 

 in the fat-soluble factor did not. The lipid substance in the plasma which 

 yields this unidentified fat-soluble factor is considered to be directly con- 

 cerned in resistance to avian malaria. Biotin deficiency produced by 

 synthetic, biotin-deficient diets decreased the resistance of chickens to 

 P. lophurae and P. cathemerium. 



Eggerth^^^ tested the action of sulfur-containing soaps (a-mercapto and 

 a-disulfo soaps prepared from caprylic, capric, lauric, myristic, palmitic, 

 and stearic acids) against Diplococcus pneumoniae, Streptococcus pyogenes, 

 Corynehacterium diphtheriae. Micrococcus pyogenes var. aureus, Pasteurella 

 multocida, and Brucella melitensis (Malta fever) and other organisms. 

 He found that the germicidal titers of the acids increased rapidly with 

 the length of the chain until a maximum was reached, and then decreased. 

 The most active soap in the series was not always the same for the various 

 organisms. At a pH of 7.5, in the a-mercapto series, mercaptolaurate 

 was most acti^'e against Micrococcus ovalis and Pstudomonas aeruginosa. 

 Mercaptolaurate and mercaptomyristate were equally active against 

 Corynehacterium diphtheriae, Pasteurella midtocida. Brucella melitensis, 

 Vibrio comma, and Salmonella typhosa (typhoid fever organism). Mercap- 

 tomyristate was most potent against Diplococcus pneumoniae. Streptococcus 

 pyogenes, and Micrococcus pyogenes var. aureus. In the disulfo series, 

 dicaprate was the most germicidal for Pasteurella multocida, Vibrio comma, 

 and Salmonella typhosa. Dilaurate was most effective against Coryne- 

 bacterium diphtheriae. Micrococcus pyogenes ^'ar. aureus. Micrococcus ovalis, 



''' G. W. Kidder and V. C. Dewey, The Biochemisirtj of CiUates in Pure Culture, in A. 

 Lwoflf, The Biochemistry and Physiology of Protozoa, Vol. /, Academic Press, New York, 

 1951, pp. 323-400 (p. 337). 



'^ W. Trager, J. Exptl. Med., 85, 663-683 (1947). 



'^' A. H. Eggerth, J. Expfl. .Med., 5S, 27-42 (1031 ). 



