NOT DESCRIBED IN PREVIOUS SECTIONS. 541 



BACILLUS LEPORIS LETHALIS. 



Obtained by Dr. Paul Gibier (1888) from the contents of the intestine of 

 yellow-fever patients; also by the writer from the same source (1888, 1889) 

 in exceptional cases and in comparatively small numbers. Named and de- 

 scribed by present writer. 



Morphology. Bacilli with rounded ends, from 1 to 3 ^ in length and 

 about 0.5 H in breadth. The length may vary in the same culture from a 

 short oval to rods which are two or three times as long as broad, or it may 

 grow out into flexible filaments of considerable length. In recent cultures 

 the bacilli are frequently united in pairs. 



Stains readily with the aniline colors usually employed. In cultures 

 which are several days old, or in recent cultures when the stained prepara- 

 tion is washed in alcohol, the ends of the rods are commonly more deeply 

 stained than the central portion " end staining"; and in old cultures some 

 of the bacilli are very faintly stained. 



Biological Characters. A.U aerobic, liquefying, actively motile bacillus. 

 Does not form spores. 



In gelatin stab cultures, at the end of twenty-four hours at a tempe- 

 rature of 20 to 22 C., there is an abundant development along- the line of 

 puncture and commencing liquefaction at the surface. Later the liquefaction 

 is funnel-shaped, and there is an opaque white central core along the line 

 of puncture, with liquefied gelatin around it. Liquefaction progresses most 

 rapidly at the surface, and in the course of three or four days the upper por- 

 tion of the gelatin for a distance of half an inch or more is completely lique- 

 fied, and an opaque white mass, composed of bacilli, rests upon the surface 

 of the unliquefied portion. 



In gelatin roll tubes the young colonies upon the surface are transparent 

 and resemble somewhat small fragments of broken glass ; later liquefaction 

 occurs rapidly. Deep colonies in gelatin roll tubes, or at the bottom of stick 

 cultures, are spherical, translucent, and of a pale straw color. 



Upon the surface of nutrient agar it grows rapidly, forming a rather thin, 

 translucent, shining, white layer, which covers the entire surface at the end 

 of two or three days at a temperature of 20 C. 



Upon potato the growth is rapid and thin, covering the entire surface, 

 and is of a pale-yellow color. 



This bacillus grows at a comparatively low temperature, and its vitality 

 is not destroyed by exposure for an hour and a half in a freezing mixture at 

 15 C. below zero (5 F.). 



Decided growth occurred in a stick culture in gelatin exposed in Balti- 

 more during the month of January in an attic room. During the twenty- 

 two days of exposure the highest temperature, taken at 9 A.M. each day, 

 was 11 C., and the lowest 2 C. At a temperature of 16 to 20 C. develop- 

 ment in a favorable culture medium is rapid. 



There is no evidence that this bacillus forms spores ; cultures are sterilized 

 by exposure to a temperature of 60 C. for ten minutes. 



Coagulated blood serum is liquefied by this bacillus. It retains its vitality 

 for a long time in old cultures, having grown freely when replanted at the 

 end of a year from a hermetically sealed tube containing a pure culture in 

 blood serum. 



Pathogenesis. This bacillus is very pathogenic for rabbits when injected 

 into the cavity of the abdomen in quantities of one cubic centimetre or more ; 

 it is less pathogenic for guinea-pigs, and is not pathogenic for white rats 

 when injected subcutaneously. Gelatin cultures seem to possess more in- 

 tense pathogenic power than bouillon cultures, and cultures from the blood 

 of an animal recently dead as the result of an inoculation are more potent 

 than those from my original stock which had not been passed through a 

 susceptible animal. 



