PATHOGENIC ANAEROBIC BACILLI. 589 



BACILLUS AEROGENES CAPSULATUS. 



Found by Welch in the blood vessels of a patient with thoracic aneurism, 

 opening- externally ; autopsy made in cool weather eight hours after death 

 the vessels found full of gas bubbles. 



Morphology. Straight or slightly curved bacilli with slightly rounded 

 or sometimes square-cut ends ; a little thicker than Bacillus aiithracis, and 

 varying in length average length 3 to 6 // ; long threads and chains are oc- 

 casionally seen. The bacilli, both from cultures and in the animal body, are 

 enclosed in a transparent capsule. 



Biological Cliaracters. An anaerobic, non-motile, non-liquefying ba- 

 cillus. Does noc form spores. Grows in the usual culture media, in the ab- 

 sence of oxygen, at the room temperature, and produces an abundant de- 

 velopment of gas in all. In nutrient gelatin there is no marked liquefaction, 

 but the gelatin is slightly peptonized. In agar, colonies are developed which 

 are usually one to two millimetres in diameter, but may attain a diameter of 

 one centimetre ; they are grayish- white in color and in the form of flattened 

 spheres, ovals, or irregular masses, beset with little projections or hair-like 

 processes. Bouillon is rendered diffusely cloudy, with an abundant white 

 sediment. Milk is coagulated in one or two days. The cultures in agar and 

 bouillon have a faint odor, comparable to that of stale glue. Upon potato a 

 pale grayish-white layer is developed; growth occurs at 18 to 20 C., but is 

 much more rapid at 30 to 37 C. Bouillon cultures are sterilized by ex- 

 posure to a temperature of 58 C. for ten minutes. 



Pathogenesis. "Quantities up to 2.5 cubic centimetres of fresh bouillon 

 cultures were injected into the circulation of rabbits without any apparent 

 effect, except in one instance in which a pregnant rabbit was killed, by the 

 injection of one cubic centimetre, in twenty-one hours. If the animal is 

 killed shortly after the injection the bacilli develop rapidly after death, with 

 an abundant formation of gas in the blood vessels and organs, especially the 

 liver. At temperatures of 18 to 20 C. the vessels, organs, and serous cavi- 

 ties may be full of gas in eighteen to twenty-four hours, and at tempera- 

 tures of 30 to 32 C. in four to six hours, when one cubic centimetre of a 

 bouillon culture has been injected into the circulation shortly before death." 



It is suggested by Welch and Nuttall that in some of the cases in 

 which death has been attributed to the entrance of air into the veins, the gas 

 found at the autopsy may not have been atmospheric air, but may have been 

 produced by this or some similar microorganism entering the circulation and 

 developing after death. 



In a paper published in the Bulletin of the Johns Hopkins Hos- 

 pital (September, 1900) Professor Welch says: " Our further studies 

 of the gas bacillus obtained from different sources have shown a 

 moderate range of variation in some of its properties. This is true 

 especially of spore formation, rapidity of liquefaction of gelatin, 

 presence of capsules, and virulence." 



This bacillus has been shown by recent researches to be widely 

 distributed in nature, its natural habitat being the intestinal canal of 

 man and lower animals and the soil. It has considerable importance 

 in human pathology, having been found in various localized infec- 

 tious processes in the subcutaneous tissues, the uterus, the urinary 

 tract, the liver, the lungs, and the pleural cavities. 



