PATHOGENIC BACTERIA. 307 



the reaction occurs varies from a few minutes to one or two 

 hours. With little dilution the time should be short; with 

 greater dilution it may be longer. Both clumping and 

 paralysis of motility should take place. In a positive case 

 the reaction should be distinct. Normal blood sometimes 

 exhibits agglutinative properties in some degree. If the 

 reaction in any case is not satisfactory it should be tried 

 with a higher dilution, i to 50, and the result should be 

 positive if the case is a genuine case of typhoid fever. 



The reaction usually appears between the seventh day 

 and the end of the third week of the disease; it may be 

 seen earlier; it is often delayed and appears late. The 

 test frequently has to be repeated when the first result is 

 doubtful or negative. Reports indicate that the method is 

 a great aid in the diagnosis of typhoid fever, though not 

 infallible. 



Considerable experience is necessary to acquire the 

 judgment needed in using this test. 



The agglutinating power becomes lessened after recovery, 

 and usually is wanting at the end of a year. Rarely it may 

 be present for a longer time, a fact that is to be borne in 

 mind in diagnosis. 



Typhoid bacilli have frequently been obtained from the 

 stools of cases of the disease, but they are isolated only with 

 considerable difficulty. At autopsies they are best culti- 

 vated from the spleen, in which, however, it is to be remem- 

 bered, the bacillus coli communis may also be present. 

 Puncture of the spleen with a sterilized hypodermic needle, 

 during life, has also been resorted to as a means of diag- 

 nosis. The drop of fluid withdrawn may be examined by 

 culture-methods for typhoid bacilli. There is probably some 

 clanger to the patient attending this procedure. Cultures 

 made from the blood, where several c.c. are taken show that 

 a few bacilli occur in the blood in a large proportion of cases 

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