68 Bulletin No. 207. 



from these two organs was then plated in gelatin and agar 

 and placed under anaerobic conditions. Several deep colonies 

 developed in the gelatin plate and were transferred to pork 

 broth. An anaerobic organism* was isolated from the caecum, 

 possessing the following characters : 



Morphology and Staining Characters: A large straight 

 rod with rounded ends, 0.8 to 1 micron wide and 2 1/2 to 6 microns 

 long. Slightly motile. Spores form in alkaline glucose pork 

 broth at room temperature. The spores are oval in shape, 

 distending the wall of the organism, and situated near the end 

 of the bacillus. The organism is Gram-positive and stains read- 

 ily with the ordinary anilin dyes. The bacilli are single but 

 may occur in short chains (Fig. 8). 



Cultivation: The bacillus is a strict anaerobe and de- 

 velops favorably in alkaline pork broth infusion at room 

 temperature. Acid medium is not favorable to its growth 

 alone in meat broth. It can be propagated under anaerobiosis 

 in alfalfa and corn silage extracts, made slightly alkaline. 

 Aerobically it develops in acid pork broth and forage extracts 

 in association with Fusarium sp. In gelatin plates the colonies 

 develop in 7 to 12 days and are round, yellowish white in color 

 and composed of coarse granules with a finely fringed peri- 

 phery (Fig. 9). In gelatin mild liquefaction occurs at the 

 edge of the colony, which in old cultures becomes diffuse. 

 Consistent development has not been observed in solid cul- 

 ture media. Glucose pork broth at room temperature is more 

 favorable for its development. Growth may appear in 2 to 3 

 days with a general clouding of the medium and gas produc- 

 tion, lasting for varying lengths of time. The medium grad- 

 ually clears, first noticeable in the upper stratum, the growth 

 settling to the bottom of the tube. Old cultures give off a 

 sour odor resembling butyric acid. 



The similarity of the morphological characters of the 

 organism isolated from the caecum of horse No. 91 (c-91) to B. 

 botulinus prompted its administration to small animals. On 

 February 14th, 1917, a guinea pig weighing 300 gms. (labo- 



*The laboratory index c-91 is employed for convenience in referring" to 

 the anaerobic bacillus isolated from the caecum of horse No. 91 fatally 

 infected by drinking- the oat hay water. 



