462 S. HENRY AYERS AXD COURTLANd S. MUDGE 



the basic media and inoculated with the streptococcus. In 

 table 4 experiment 3 we see a most astonishing stimulation of 

 growth. 



Another interesting phenomenon was observed which might 

 well be mentioned at this point. In 1918, Mr. Johnson of these 

 laboratories prepared in the field, some pasteurized-cream butter 

 without salt and also separated some of the butterfat free from 

 casein. These were sealed in sanitary cans and sent to Washing- 

 ton. Since then they have been in our incubators at tempera- 

 tures averaging 30°C. These cans were opened recently and 

 the fat found to be in a melted condition. Samples were taken 

 of the supernatant fat from a butter can and also some of the 

 oil from the can of butterfat free from casein. Media were made 

 with these two fats using 1 per cent. The results which are 

 also shown in table 4 are peculiar to say the least. The fat from 

 the butter itself seems to be toxic but the stored fat free from 

 casein stimulated bacterial growth the same as our fresh butter- 

 fat. One other point of interest is that the stimulating effects 

 of fats and oUs was not manifest to any degree in a plain peptone 

 medium but was evident in the yeast peptone medium. 



It was found by the addition of methylene blue that an anero- 

 bic condition did not exist in the media with fats and oils. It 

 cannot be assumed therefore that an anaerobic condition was 

 responsible for the stimulation of the growth of the strepto- 

 coccus. 



The experiments with fats and oils show one thing definitely 

 which is that very small amounts of these materials stimulate 

 in a most remarkable manner the growth of a streptococcus 

 growing in a yeast peptone medium. If our studies had been 

 limited to butterfat and cod-Uver oil strong evidence could have 

 been presented as to the stimulation by fat-soluble A. But 

 the stimulating effect of mineral oils and even soUd paraffin 

 change the aspect of the situation. 



Our results as we see them permit of one of three possibilities, 

 first, that the growth-promoting property of fats and oils is not 

 due to the fat-soluble A, or second, that if fat-soluble A is re- 

 sponsible then it must be contained in mineral oil. The second 



