In more than 90 per cent. of cases of enteric fever a positive reaction may be obtained by means of Widal's reaction; in more than 99 per cent. of these eases examined between the fourth and seventh day, inclusive, a positive reaction may be obtained; in more than 3 per cent. of diseases other than enteric fever a re action is produced indistinguishable from the typical typhoid reaction; and a negative reaction is obtained with the blood of healthy persons who have not had enteric fever lately. J. C. Da Costa (N. V. Med. Jour., Aug. 21, '97).
From a practical point of view the re action can, in general, be detected in typhoid patients from the first day of the disease onward. It may at times be delayed, but is only exceptionally ab sent: 1 ease in 177, according to my figures. One can hardly expect more from a method based on a bacteriological reaction always subject to individual and unforeseen variations. Widal (Brit. Med. Jour., Dec., '97).
The agglutination-test is of the utmost importance in filially settling the diag nosis in doubtful cases. It is a good rule to treat all doubtful cases in which, for a time, the differential diagnosis be tween subacute or acute nephritis and enteric fever cannot be made, as acute cases of enteric fever. J. C. Wilson (Amer. Jour. Med. SM., Dec., '95).
The \Vidal reaction in typhoid fever does not permit an early unequivocal di agnosis of the disease. The reaction is an immunity reaction, and not merely a reaction of infection. Due attention being given to the severity of the case, the stronger the reaction, the more favor able is the prognosis. The test has been personally made in 51 individuals who had had typhoid fever. In 20 eases the reaction was positive during the first year after the disease, and in 11 negative. Of those examined more than a year after the fever, 6 were negative and 11 were positive, 1 each after 14, 15 and 17 months, and 3 after 2 after 4 and 1 each after 5, 10, 15, and 21 years. Of the cases in the first year after the disease, 64.5 per cent. were positive. Of 11 cases from the second to the fifth years after the disease, S, or 72.7 per cent., were positive. If in a case sus pected of typhoid fever, the reaction is very strongly positive, it is connected with the present illness, and not with a former attack of the disease. In chil
dren under seven years the reaction is feebler than in older persons, and it disappears earlier; nevertheless, it is, in children, perhaps the most valuable sign of typhoid fever. Basel and Mann (Miinch. med. Woch.. May 2, '99).
In forty tests for the \Vidal reactions made on soldiers from the Spanish American War at the Brooklyn Hospital, this reaction was obtained in all, and the cases went through a typical typhoid.
In one suspected typhoid it was not ob tained; on examining the blood, Layer an's plasmodium malarim was found. The case responded promptly to quinine. .1. M. Van Cott (Brooklyn Med. Jour., Feb., 1900).
During the last year at the Boston City Hospital it has been the custom to perform the \Vidal test more frequently than at first, and it has been found that, while the reaction sometimes appeared at a very late period, — twenty or twenty-five days from the onset of the fever, — nevertheless it was generally eventually obtained.
The method of applying the test has been the following: A few drops of blood have been drawn from the pa tient's ear into a small section of glass tubing. sealed at one end by heat and left open at the other. After the serum has separated, 1 drop of it is mixed with 10 drops of an active culture of typhoid bacillus twenty-four to thirty six hours old. The dilution is, there fore, 1 to 11, or 9 per cent. For a con trol, a few drops of an unmixed culture are usually put en the other end of the slide. If immobility and clumping are present in the serum-culture mixture in course of one-half hour, the reaction is reported as positive, otherwise not. In the majority of eases the reaction ap pears in ten to fifteen minutes.
At the City Hospital during a period of six months, from May 25 to Novem ber 2S, 1000, there were 2.53 cases of typhoid fever in the hospital, which were tested, repeatedly, by the \Vidal reaction. in all eases until a positive result was obtained. In 10 of these cases there was a constant absence of \Vidal reaction, or 4 per cent. of fail ures.
A typical instance of the tardiness of the \Vidal response is illustrated in 1 case, where, after eight consecutive fail ures, it was positive for the first time on the twenty-ninth day. C. F. With ington (Boston Med. and Surg. Jour., May 9, 1901).