CHOLERA VIBRIO 573 
and examine the contents of the tubes for granulated and partly 
dissolved organisms after intervals up to two hours. The test is 
carried out as follows: a series of dilutions of fresh immune serum, 
1 to 50 to 1 to 500, is prepared in small sterile test-tubes, 0.5 cc. to 
each tube. A suspension of cholera vibrios, one loopful of an eighteen- 
hour agar slant growth to 1 cc. of sterile salt solution, is also prepared; 
usually 10 cc. are sufficient. This is thoroughly shaken and 0.5 cc. 
added to each tube of diluted serum. Control tubes of normal serum 
and bacterial suspension are incubated under parallel conditions. 
The entire set of tubes is incubated at 37° C. and examined at intervals 
up to four hours. The control tubes swarm with vibrios. The immune 
serum tubes up to the limits of potency contain vibrios in various 
stages of solution. Only true cholera vibrios will be thus dissolved. 
The various cholera-like vibrios are unafl'ected. 
The bacteriological diagnosis of the cholera vibrio is one of the 
most difficult known to bacteriology. The large number of closely 
related forms introduces complications in the diagnosis which have 
frequently led to error. In general it may be stated that a vibrio 
which agglutinates ^^oV o ^^'ith a specific anticholera serum of high 
potency, and exliibits the Pfeifl'er phenomenon in a perfectly typical 
manner may be safely diagnosed as positive. Departure from this 
standard should cause the organism to be regarded with suspicion, 
but should not lead to relaxation of appropriate hygienic measures in 
relation to the case. 
5. Complement-fixafiun.—Besche and Kon,^ Neufeld and Haendel.- 
and others have been successful in diagnosing cholera and identifying 
cholera vibrios by means of the complement-fixation test. This method 
has not been generally used, however. 
6. Agcilutination by Seriim of Patient.— The agglutination reaction 
is not of much value for an early diagnosis of Asiatic cholera. Agglu- 
tinins occasionally appear in the blood serum of cholera patients 
as early as the third or fourth day; usually, however, they are not 
demonstrable until later. A dilution of at least 1 to 50 should be 
obtained with the patient's serum to warrant a positive diagnosis. 
Even in chronic cases and in cholera carriers this reaction is too 
inconstant to serve practical needs.'' 
Dissemination.— Cholera vibrios are foimd in the fecal discharges 
of cholera patients, but practically never in the urine, so far as is 
known. The disease is spread through contaminated water and 
sewage, occasionally by uncooked vegetables and by fomites, rarely 
by milk. Dissemination by flies is probably fairly common, particu- 
larly in those countries, as India, where the dejecta are not properly 
disposed of. Passek"* has found cholera A'ibrios numerous, and of 
> Ztschr. f. Hyg., 1909, 62, 161. 
■ Arb. a. d. kais. Gesundamte, 1907, 26, 536. 
' Indian .Tour. Med. Research, 1915, 2, No. .3. 
' Centralbl. f. Bakteriol., ref., 1911, 49, 697. 
