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 anthracis, and 
varying in length—average length 8 to 6 w; 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 Characters.—An anaérobic, non-motile, non-liquefying ba- 
cillus. Does not 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 inall.. 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 culturesin agar and 
bouillon have a faint odor, comparable to that of stale glue. Upon potatoa 
pale grayish-white layer is developed; growth occurs at 18° to 20° C., but is 
much more rapid at 80° to 87° 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 microdrganisiu 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. 
