DEMONSTRATION OF CHOLERA VIBRIO. 373 



Gruber-Durham test, which is to be looked upon as the most certain 

 reaction which we possess up to this time (see below). 



With a negative result in these examinations cholera may still be 

 present, for in very rare cases the occasional absence of vibrios from 

 the stools of undoubted cases of cholera has been proved. Thus, for 

 example, Rumpel failed to demonstrate the vibrios in the first 50 c.c. 

 of rice-water stool from a fresh typical case of cholera. 



B. In suspected water. 



The water in question is placed in half-filled flasks in quantities of 

 500 c.c. to 1 liter, together with so much of a strong peptone chlorid 

 of sodium solution (20 % peptone, 10 % NaCl) that the water contains 

 \% of peptone; and to this is added also alkali in excess (26 c.c. 

 normal sodium hydroxid, \% crystalline or 0.3% anhydrous soda). 

 The further examination is carried out exactly as in A, 2-6. Great 

 skepticism is demanded in water examinations. 



As especially shown by the detailed work of Dunbar, we may 

 from the first exclude a great number of vibrios resembling cholera in 

 the diagnosis of cholera by means of gelatin plates, potato cultures, 

 photogenesis, etc. ; but there were a considerable number of cultures, 

 in which all morphologic and biologic means of separation were lack- 

 ing, which were pointed out by the serum reaction, exactly analo- 

 gously to the typhoid-coli diagnosis. 



This was carried out according to Pfeiffer's method (Z. H. xix, 

 75; xx, 198), since at the time of the last active interest in cholera 

 the Gruber-Durham reaction was still undiscovered. Here, unfor- 

 tunately, all the cultures were excluded which proved to be non-patho- 

 genic for experimental guinea-pigs, and which could not be rendered 

 viulrent by means of the introduction of definite, large doses into 

 animals. (Compare p. 95.) 



The cholera serum which is used for these investigations is obtained 

 as follows : A rabbit weighing 1.5 to 2 kilos is injected subcutaneously 

 with the culture substance from three slanted agar cultures (twenty- 

 four hours, 37), together with about 5 to 6 c.c. of bouillon. The 

 animal becomes somewhat feverish, and on the sixth day is bled, and 

 yields, following the directions on page 105, an active serum, which 

 keeps for months in a dark ice-box if 0.5% phenol is added. l 



Pfeiffer indicates the working strength of serum as follows : He 

 designates as a titer of serum the smallest quantity of serum which 

 certainly suffices to cause solution of 2 mg. of living normal culture 

 inside of an hour, if it is mixed with 1 c.c. of bouillon and injected 

 into the abdominal cavity of a young guinea-pig weighing 200 gm. 

 The most active guinea-pig serum had 0.5 mg. to the titer. (Serum 

 from four convalescent cholera cases in man had 2. 5 to 20 mg. to the 

 titer. ) 



Of this serum, now, about 10 to 30 mg. (ten times the minimum 

 efficient dose), together with 1 c.c. of bouillon and a loopful of viru- 

 lent cholera vibrios, are introduced into the peritoneal cavity of a 



1 If cholera serum is generally introduced as a diagnostic aid, then 

 reliable firms or State institutes must undertake its preparation. 



