YELLOW FEVER 669 



widespread interest they aroused among bacteriologists. Comil and 

 Babes,' in 1883, described chained cocci to which they attributed etio- 

 logical significance, but their contentions have remained entirely un- 

 confirmed. Sternberg,^ in 1897, described a colon-like organism, " bacil- 

 lus X," for which he made very conservative claims, which he himself, 

 later, withdrew. 



The most active discussion was aroused by the announcement of 

 SanareUi,' in 1897, that he had discovered, in the blood and tissues of 

 patients dead of yellow fever, a Gram-negative bacillus, which he be- 

 lieved to be the etiological agent of the disease. He based his contention 

 upon the facts that he had isolated the organism from seven cases of 

 yeUow fever, had produced symptoms similar to the disease of the human 

 being by the inoculation of pure cultures into dogs, and had obtained 

 agglutination of the bacillus in the serum of convalescent patients. Later 

 he inoculated five human beings subcutaneously with sterilized cultures 

 of this "Bacillus icteroides," and obtained symptoms which he believed 

 simulated closely those of yellow fever. The claims of Sanarelli at first 

 found much apparent confirmation, but later work by Durham and 

 Myers,* Otto,^ Agramonte," and others has definitely refuted his original 

 claims, and there is to-day no scientific basis for the assumption that 

 the Bacillus icteroides has any etiological relationship to the disease. 

 Protozoan incitants, also, have been described by Klebs,' Schiiller,* 

 Thayer ,° and others, without bringing conviction or even justifying 

 extensive investigation of their claims. 



While thus the causative agent of yellow fever remains undiscovered, 

 some of its biological properties are known. Reed, Carroll, Agramonte, 

 and Lazear'" were able to show that the infecting agent is present in 

 the blood serum of patients during the first three days of the disease 

 and that it could pass through the pores of Berkefeld filters. Such 

 filtered serum remained infectious for human beings — a fact which de- 

 monstrates that the incitant is extremely small and possibly ultra- 



' Cornil and Babes, Comptes rend, de I'acad. des sci., 1883. 



2 Sternberg, Cent. f. Bakt., I, xxii, 1897. 



3 Sanarelli, Ann. de 1' inst. Pastevir, 1897, and Cent. f. Bakt. , I, xxii, xxvii, and xxix. 

 * Durham and Myers, Thompson Yates Laboratory Reports 3 1902. 



'Otto, Vierteljahrsch. f. gericht. Medizin, etc., 27, 1904. 



' Agramonte, N. Y. Med. News, 1900. 



' Klebs, Jour. Am. Med. Assn., April, 1898. 



» Schilller, Berl. klin. Woch., 7, 1906. 



9 Thayer, Med. Record, 1907. 



" Reed, Carroll, Agramonte, and Lazear, Phila. Med. Jour., 1900, 



