Abstract
Summary. Quantitative methods were used to study the microflora of faeces produced by a group of baboons receiving fresh fruit and vegetables (natural diet), and 3 groups fed a synthetic diet deficient in either pyridoxine or riboflavin, or which contained both vitamins (pair fed). There was no significant difference between the microbial counts of any of the groups of organisms studied in the pyridoxine or riboflavin deficient and pair fed baboons. Compared with baboons on natural diet, faecal counts from baboons fed the synthetic diet showed highly significant increases in Clostridium welchii and in lactose‐fermenting enterobacteria, together with a considerable decrease in the number of lactobacilli. Small increases in the numbers of micrococci, staphylococci and faecal streptococci were noted, whilst the numbers of yeasts were reduced slightly. Whilst the change from the natural to the synthetic diet caused a great alteration in the flora, the synthetic diet flora appeared to be extremely stable and generally unaffected by drastic modifications of the synthetic diet. However, marked alteration did occur on re‐feeding with the natural diet. Data on the faecal microflora of baboons are compared briefly with published data for man and other animals, and the effects of dietary changes on the composition of the faecal flora are discussed.