280 BACILLUS TYPHOSUS. 



ally lose their motility, and then they are seen to gather in 

 small bunches or clumps (Fig. 128). The more marked this 

 clumping and loss of motility, and the earlier the reaction 

 occurs, the more positive is the diagnosis. Ordinarily this 

 reaction begins to be noticed in about half an hour, but in 

 some instances it does not appear before an hour or two. 

 If the blood contains little agglutinating substance, the reac- 

 tion does not occur until late and is not characteristic. When 

 blood other than typhoid is mixed with the typhoid culture, 

 the bacilli may lose their motility, but the loss of motility is 

 never complete nor is the clumping perfect. Some experience 

 is necessary before any degree of efficiency is attained in 

 interpreting this phenomenon. The typhoid culture should not 

 be more than twenty-four hours old, and should be virulent. 

 Bouillon cultures should always be used. It is not necessary 

 to sterilize the blood-serum obtained from the patient. 



Examination of water for typhoid bacilli : In the examina- 

 tion of water for the Bacillus typhosus, its resistance to car- 

 bolic acid is a valuable aid in its isolation. From 0.05 to 

 0.25 per cent, of carbolic acid is added to the suspected water. 

 Gelatin plates are made from this water according to the 

 method of Eisner. As the specimen of water may contain 

 only a few bacteria, it is necessary that many examinations 

 be made. The examination can be facilitated by adding 20 

 c.c. of a standardized, sterilized, concentrated solution of 

 peptone and sodium chloride to 100 c.c. of carbolized water. 

 The mixture is placed in the incubator, and in about twenty- 

 four hours gelatin plates are made from this mixture. Any 

 growth which takes place is either the typhoid or colon 

 bacillus. The differentiation is made as described above. It 

 is advisable to make several tests at the same time, as that 

 will still further facilitate the work. 



Prophylaxis : The prophylaxis in typhoid consists of the 

 strictest antiseptic precautions. All the intestinal discharges 

 and urine must be disinfected at once and thoroughly as 

 described in the chapter on Disinfection. The same is true 

 of soiled linen or clothing. The attendants must be careful 

 not to infect themselves by coming into direct contact with 

 infective material. Reinfection of the patient is avoided by 



