Morphology 533 



constant presence of any particular micro-organism in the 

 blood and tissues of yellow fever cadavers. The micro- 

 organism most frequently encountered was Bacillus coli 

 communis. 



The most interesting micro-organism met with was 

 Bacillus x, which he isolated from a considerable number 

 of cases, and may have been present in all. It was not 

 present in any of the control experiments. It was very 

 pathogenic for rabbits when injected into the abdominal 

 cavity. Sternberg says : "It is possible that this bacillus is 

 concerned in the etiology of yellow fever, but no satisfactory 

 evidence that this is the case has been obtained by experi- 

 ments upon the lower animals, and it has not been found in 

 such numbers as to warrant the inference that it is the 

 veritable infectious agent." It is so similar to Bacillus icte- 

 roides that they may be identical. 



BACILLUS ICTEROIDES (SANARELLI). 



General Characteristics. An actively motile, flagellated, non- 

 sporogenous, non-liquefying, non-chromogenic, aerogenic, aerobic and 

 optionally anaerobic, pathogenic bacillus which stains by the ordinary 

 method, but not by Gram's method. 



Sanarelli regarded this bacillus as the specific organism of 

 yellow fever. He found it in 1 1 autopsies upon yellow 

 fever cases, but always found it associated with strepto- 

 cocci, colon bacilli, proteus, and other organisms. It is 

 found in the blood and tissues, and not in the gastro- 

 intestinal tract, and by proper methods isolation of the 

 organism was possible in only 58 per cent, of the cases, 

 and in rare instances was accomplished during life. 



Distribution. By suitable methods it can be found in 

 the organs of yellow fever cadavers, usually aggregated in 

 small groups, in the capillaries of the liver, kidneys, and 

 other organs. The best method of demonstration is to 

 keep a fragment of liver, obtained from a body soon after 

 death, in the incubator at 37 C. for twelve hours and 

 allow the bacteria to multiply in the fresh tissue before 

 examination. 



Morphology. The bacillus presents nothing morpho- 

 logically characteristic. It is a small pleomorphous bacillus 

 with rounded ends, usually joined in pairs. It is 2-4 fi. in 

 length, and, as a rule, two or three times longer than broad 



