282 BACILLUS TYPHOSUS. 



Furthermore, the people are cautioned against unhygienic 

 surroundings, damp, dirt, garbage, and neglect of personal 

 cleanliness. 



Immunization : It is possible to immunize animals to typhoid. 

 Rabbits are injected with gradually increasing doses of either 

 living or dead typhoid bacilli until the desired degree of 

 immunity has been attained. The blood-serum of such rabbits 

 is bactericidal and also slightly antitoxic. Several investiga- 

 tors have observed that the blood-serum of persons convales- 

 cent from typhoid fever possesses the same properties as the 

 blood-serum of immunized animals. 



It is a matter of record that typhoid fever rarely attacks 

 the same individual more than once, so that the inference can 

 be made that one attack confers immunity. The blood-serum 

 of typhoid patients possesses immunizing properties when 

 injected into animals inoculated with typhoid bacilli. 



Preventive inoculation with sterilized cultures of typhoid 

 bacilli appears to be of considerable value. All the reports 

 made show that by far the greater majority of persons inocu- 

 lated in this manner did not acquire the disease. The inocu- 

 lation is followed by a febrile reaction, which lasts for about 

 one day, and which produces the agglutinating substance in 

 the blood. The inoculation should be repeated in about two 

 weeks. A dose of 0.75 c.c. of the serum is given at each 

 inoculation. 



The blood-serum of typhoid convalescents, as well as steril- 

 ized cultures, have been used for curative purposes in typhoid 

 fever, but the results have been of such a nature that it is 

 impossible at this time to pass any opinion on the serum 

 treatment of typhoid fever. One investigator used a glycerin 

 extract of the thymus, spleen, bone-marrow, brain, and spinal 

 cord of animals dead of typhoid, and reported extremely 

 gratifying results from its use in eighteen cases. Other clini- 

 cians report a decided falling off in the mortality, and also a 

 much shorter duration of the disease. 



