1390 THE ENTEROIDEA GROUP OF TROPICAL FEVERS 



Macroscopic tests (sedimentation test) are also in use, and various 

 forms of apparatus (agglutinometers) can be obtained, which enable 

 the general practitioner to carry out the test himself without using 

 a microscope. A convenient rapid method is Alcock's, the blood 

 being diluted very little and examined after only a few minutes. 

 Dreyer's method, using specially standardized emulsions, is useful, 

 as this method renders much easier the making of agglutination 

 curves, which are of great practical importance in the diagnosis 

 of enteric in inoculated individuals. Technical details may be 

 found in any modern textbook on bacteriology. 



In the tropics, even at the present time, one is apt to be asked what value 

 is to be placed on the result of the agglutination reaction. Some medical 

 practitioners are inclined to be sceptical, while others tend to base their 

 diagnosis solely on the result of the test. We would emphasize the fact that 

 in enteric fever, as in any other bacterial disease, in order to come to a definite 

 diagnosis the results of the clinical examination and those of the laboratory 

 must not be dissociated. 



The practitioner should give his attention to the following points: — 

 Reaction Negative. — (i) The reaction is generally absent during the first 

 week of the disease. 



(2) In some very rare cases — in our experience generally of very malignant 

 type — the test may remain negative during the whole course of the malady. 



(3) The reaction with the B. typhosus — which in certain tropical labora- 

 tories is still the only bacillus of the typhoid group used for the test — is 

 negative in two varieties of enteric fever — paratyphoid A and paratyphoid B. 



Reaction Positive. — (i) When the reaction is positive, it should be remem- 

 bered that the blood may contain specific agglutinins many years after an 

 attack of typhoid is over. In the event of fever in such a case the medical 

 man who would solely rely on the Widal test would easily fall into error. 



(2) The reaction is not rarely positive in cases of jaundice, but recent 

 researches have demonstrated the fact that these cases are in reality often 

 due to the colecystitis caused by B. typhosus. 



(3) The reaction is positive in vaccinated persons for a variable period of 

 time after inoculation. 



(4) One must be sure that the test has been carried out with sufficiently 

 diluted blood. A dilution of i in 40 is sufficient for ordinary purposes. 



H^MOCULTURES.- — Two methods may be used- — the so-called 

 ' dilution method,' introduced by Castellani in 1898, and the ' bile- 

 enrichment method,' introduced by Drigalski and Conradi, and 

 modified by many authors. The latter is at the present time to be 

 preferred, being simpler. The former is still of use when a mixed 

 infection is suspected, as, for instance, a typhoid-pneumococcus 

 infection. The pneumococcus and many other germs would grow 

 very badly, or not at all, in bile media. 



Castellani' s Dilution Method. — The region of the bend of the elbow 

 is cleaned with spirit or ether, then disinfected with perchloride 

 lotion (i in 1,000), then a little spirit or ether is poured again on 

 the skin, or the region may be simply painted with tincture of iodine. 

 When this has become dry, a few c.c. (2 to 5) of blood, by means of 

 a sterile all-glass syringe, are taken aseptically from a vein of the 

 region, generally the median basilic. The blood is immediately 

 added to several large sterile flasks (at least three), each containing 



