BACTEEIUM COLL 243 



etc., thxis producing a mixed infection (Stern, Berl. klin. 

 \A^ochenschr. , 1897, 225). Thus the serum of patients 

 (in distinction to animal serum) can be employed as a 

 test for typhoid bacteria only when it has been previously 

 found entirely or almost without effect upon known Bact. 

 coli. 



Eegarding the relation of the Bact. coli to the Bact. typhi there has 

 been much work done and still more written. Objectively considered, 

 the case is that numerous things speak for the probability that the 

 Bact. typhi may originate from the Bact. coli by a loss of certain zymo- 

 genic and the acquisition of pathogenic properties, but the possibility 

 of such a change is not proved by any experimental investigation. 

 We may believe what we will, but for the present the Bact. coli 

 and Bact. typhi are two difierent organisms. Nothing pertinent to 

 the question is afiorded by the demonsti'ation, coming from various 

 sides, that the Bact. coli may lose its ability to produce indol and 

 coagulate milk. Also, the circumstance that Peekham (Jour. f. ex. 

 Med., 1897, II, 549; C. B. xxill, 986) was able to stimulate typhoid 

 bacteria to vigorous production of indol, and that cultures absolutely 

 like typhoid are found which present no agglutination with typhoid 

 serum, do not certainly prove the transformation of one kind into the 

 other, but only point to an extraordinarily close relationship. 



Bacterium coli (Escherich). L. and N. 



(Plates 18 and 19.) 



Synonym. — Bact. coli commune Esch. (Darmbacterien 

 des Sauglings, Stuttgart, 1886). Compare page 250 and 

 forward. 



Literature. — Kiessling, Sammelreferat (Hygien. Eundschau, 1893, 

 III); Losener (A. G. A. xi, 207); Germane and Maurea (Ziegler's 

 Beitrage, xil, 494 ; C. B. xv, 60) ; Tavel and Lanz (C. B. xiv, 705); 

 Von Stooklin (C. B. xvi, 130); Gordon (Jour, of Path, and Bact., 

 IV, 438). 



Common Names. — Colon bacillus, Coli bacillus, 

 "Coli Escherich." 



Microscopic Appearance. — According to the nutrient 

 medium and the age of the culture, the B. coli occurs as 

 almost isodiametric, oval forms, or (and as a rule) as 

 short rods, 2 to 4 // long and 0.4 to 0.6 m broad ; more 

 rarely in the form of shorter or longer threads. The ends 

 are rounded; not infrequently two rods lie together in 

 pairs ; also chains of bacilli occur. In unfavorable con- 

 ditions (old potato cultures, soda bouillon) there occur 



