December 28, 1906.] 



SCIENCE, 



859 



SPECIAL ARTICLES. 



CHARACTER OF THE BACTERIAL FLORA OF CAR- 

 NIVOROUS AND OF HERBIVOROUS ANIMALS. 



In the course of the study of anaerobes of 

 the human intestine it appeared desirable to 

 learn something about the characters of the 

 bacterial flora inhabiting the large intestine 

 of various domestic and wild animals. It was 

 noticed that in the dog, which is frequently 

 exclusively carnivorous, the intestinal contents 

 often showed the presence of large numbers of 

 spores, spore-bearing bacilli and vegetative 

 forms of anaerobes. The numbers present in 

 the feces were noted to be especially large in 

 some animals which had been exclusively fed 

 on meat. A study of a grown cat fed upon 

 raw meat showed the presence of Gram-posi- 

 tive vegetative anaerobes from one end of the 

 digestive tract to the other. Flora derived 

 from the stomach, small intestine and large 

 intestine were inoculated and grown in bouil- 

 lon flasks and showed an abundant production 

 of methyl mercaptan as well as hydrogen 

 sulphide. The numbers of colon bacilli pres- 

 ent in this case were relatively small as com- 

 pared with the anaerobes. The study of the 

 colonies obtained on anaerobic plates showed 

 that a large portion of the organisms present 

 in the intestinal tract were B. aerogenes cap- 

 sulatus. Intravenous infusion of these organ- 

 isms into a rabbit which was afterwards killed 

 and incubated showed in a high degree the 

 typical gas-formation.^ 



Observations on other cats showed the pres- 

 ence of considerable numbers of spore-holding 



^ The incubation method of Welch and Nuttall 

 is based on their observation that the gas bacillus 

 produces gas abundantly in the blood, organs and 

 tissues of rabbits killed a few minutes after in- 

 travenous injection. Here the blood and tissues 

 of the rabbit act as a peculiarly favorable culture 

 medium for the growth of the gas bacillus, the 

 latter having been thoroughly spread by the blood 

 through the body, and the conditions being 

 anaerobic. A suspension of the feces to be tested is 

 prepared by grinding 1 gram of the fresh material 

 with 9 CO. of 0.85 per cent, salt solution and 

 filtering through absorbent cotton. One or two 

 cubic centimeters of this suspension are then in- 

 jected intravenously into a rabbit which is quickly 

 killed and incubated for five hours at 70° 0. 



bacilli and free spores, sometimes in chains, 

 in addition to vegetative forms of anaerobes. 

 The position of these spores and spore-holding 

 bacilli has not been established in a bacterio- 

 logical sense. Observations were also made 

 upon the intestinal contents of the wolf, tiger 

 and lion. Several different tigers were studied 

 and the observations were not confined to the 

 examination of one lion and one wolf. The 

 material from the lion showed the presence of 

 many free spores. It also showed the presence 

 of considerable numbers of Gram-positive 

 bacilli, suggesting B. aerogenes capsulatus. 

 Gram-stained preparations from wolves showed 

 findings similar to those observed in the lion 

 except that the spore-holding bacilli were more 

 numerous. The findings in the case of sup- 

 posedly healthy tigers were not essentially 

 different from those in the case of the wolf 

 and lion. In the case of one tiger, suffering 

 from osteomalacia, greatly impaired nutrition 

 and loss of strength, the microscopical fields 

 derived from several different samples of feces 

 revealed the presence of immense numbers of 

 free spores and smaller numbers of immature 

 Gram-negative spore-holding bacilli. These 

 spores developed into organisms which pos- 

 sessed all the generally known cultural and 

 biochemical characters of B. aerogenes cap- 

 sulatus, including the ability to develop a 

 high grade of gas-formation in rabbits in- 

 jected and incubated. 



It was found that bouillon cultures of the 

 mixed fecal flora from the lion, tiger, wolf 

 and cat all developed quickly a sufficient quan- 

 tity of methyl mercaptan to give promptly a 

 very well developed reaction with isatin-sul- 

 phuric-acid. 



Experiments were made with the mixed 

 fecal flora from these carnivorous anim-als to 

 determine their pathogenicity when injected 

 into the subcutaneous connective tissue. It 

 would have been better to have worked with 

 pure cultures of the anaerobes in question, 

 but opportunity has not yet arisen to isolate 

 them. The result of the inoculations into 

 guinea-pigs was the same in each instance. 

 The animals died within twenty-four hours 

 and usually in fifteen to eighteen hours. At 

 autopsy the subcutaneous connective tissues 



