J. E. GRAHAM.] At present the serum for the test is obtained in three ways: from the fresh blood, from the dried blood, and from the fluid of a superficial blister. The first method is the one to be preferred, if possible, for counting leucocytes. The pipette of an ordinary Thome-Zeiss hmmocytometer may be used and enough drawn up to half-fill the capillary tube, then sufficient sterilized broth is taken up to fill the bulb. In this way a solu tion of blood-serum 1 to 20 is obtained. The solution is passed into the tube of an hmnatokrit and the corpuscles sep arated. A drop of the solution is then added to a drop of the culture, making a strength of 1 in 40, and placed under the microscope. When typhoid fever is present the movements of the bacilli cease, and clumping takes place in from a few minutes to half an hour.
A macroscopical test may be made by adding the blood or serum to a young culture of the typhoid bacillus, when the reaction begins in about two hours. The turbid liquid becomes clarified and a sediment forms of accumulated bacilli. (Osler.) At the hospital in Milan during the last thirty years typhoid fever has been mistaken for acute tuberculosis 52 times, and tuberculosis for typhoid 90 times. A simpler test than Widal's consists in ob serving the behavior of 20 to 30 drops of blood drawn from the fingers of the patient into a small test-tube and al lowed to remain at rest for twenty-four hours. When the resulting coagulum is observed, it is found that in typhoid hardly any serum is formed, the clot is not retracted. In tuberculosis there is marked retraction of the clot from the sides of the tube, and abundant forma tion of serum. Carlo Bareggi (Gazz. degli Osped., Mar. 12, '99).
To Wyatt Johnson belongs the honor of introducing the method of examining the dried blood, which has done so much to make this means of diagnosis of so much practical value to physicians both in the city and country.
Result of 297 examinations using dried instead of liquid blood-serum. The pre liminary drying of the blood did not seem to interfere with the production of the reaction, and enabled the attending physician to transmit the samples from a distance. The following conclusions
were arrived at: 1. The use of dried blood-scrum has given us what appear to be satisfactory results for diagnostic work. 2. Complete reaction was rarely delayed beyond the fifth day. 3. A complete reaction was obtained as early as the second clay. 4. Typhoid blood al lowed to dry sixty days still gave the typical reaction. Johnston and McTag gart (Brit. Med. Jou•., Dec. 5, '96).
The agglutinative action of serum tested throughout the different stages in twenty-one cases of typhoid fever. The curve of the reaction throughout the whole course of the illness is a variable one; it is sometimes slightly marked at first, and increases progressively, or it may remain the same all through. As a rule, it diminishes more or less rapidly during convalescence or even during deferveseence with remarkable rapidity, but exceptionally it lasts for months or years. Widal and Siceard (Science M6d., Feb., '97).
The method of serum-diagnosis of typhoid fever is of great practical value. The alteration of the blood on which this method is based is a specific effect of infection or intoxication with the typhoid bacillus. The microscopical se•um-test is to be preferred to the macroscopical methods. Quantitative de terminations, relating especially to the culture, the time-limits, and the dilution of the serum, are of importance, and, at least in doubtful eases, should not he neglected. As the reaction may be de layed or occasionally absent, a negative result of the test does not exclude the diagnosis of typhoid fever. The persist ence of the reaction, sometimes for years, after recovery from typhoid fever, is to be borne in mind in interpreting the re action in febrile conditions. The ap pearance of the reaction and its increase during the period of observation speak for fresh typhoid infection. The danger of mistakes from positive reactions in non-typhoid cases can be guarded against in nearly all cases. William II. Welch (Journal Amer. Med. Assoc., Aug. 14, '97).