158 APPLIED BACTERIOLOGY 



against a somewhat larger dose of B. coli than normal 

 serum, and coli serum protects against a somewhat larger 

 dose of typhoid bacilli than normal serum. By this some- 

 what increased protection the family resemblance of the 

 two kinds of bacilli is manifested. (6) The specific sera 

 do not protect against the substances contained within the 

 bodies of dead bacilli to a greater extent than does normal 

 serum. (7) By injection of normal serum into the ab- 

 dominal cavity of guinea-pigs, and twenty-four hours later 

 twice the fatal dose of dead bacilli, guinea-pigs may be 

 immunised within two weeks against a hundred times the 

 fatal dose of living typhoid bacilli. (8) If less than the 

 fatal dose of typhoid bacilli be given at the first injection, 

 and afterwards increasing multiples of the fatal dose be 

 given, guinea-pigs may be made within forty-eight hours 

 to withstand a hundred times the fatal dose (forced im- 

 munisation). (9) By injection of 0'5 to 1 c.c. of a power- 

 ful typhoid serum, animals which have been inoculated 

 intraperitoneally with thrice the fatal dose of typhoid 

 bacilli may be rendered immune to an infection that kills 

 the control animal in twenty hours, even if the injection 

 of the protecting serum have been delayed eight hours. 



Practical Disinfection. — The stools should be received into a 

 solution of mercuric chloride (1 in 500) or into a solution of 

 bleaching-powder (6 ounces to the gallon), and all particles 

 of excreta should be removed from the anus with cotton- 

 wool moistened with one of these liquids. Soiled linen' 

 must be soaked in the solution for an hour, and then well 

 rinsed in clean water ; the disinfection of the nurses' hands 

 should be rigidly insisted on, and they should eat all their 

 food only with knife, fork, and spoon, touching nothing 

 with the hands. This last precaution is most important, 

 and must be rigidly adhered to in all cases. 



