382 THE TYPHOID BACILLUS 



on the use of bacillary extracts are complicated and do not seem to offer 

 any particular advantages over those just considered. 



(a) Wassermann's method. An emulsion of cultures on agar is made in 

 distilled water, heated to 60 C. for 24 hours, macerated for 5 days at 37 C., 

 filtered through porcelain and dried in varuo at 35 C. A single inoculation 

 is given consisting of 0*0017 gram of the powder. 



(/3) Neisser and Shiga's method. An emulsion of cultures on agar is made, 

 sterilized at 60 C., macerated at 37 C. for 3 days, and then filtered. The 

 filtrate without further preparation is used as a vaccine. 



(7) Bassenge and Mayer's method. A filtrate of living cultures is used. 

 Make an emulsion in distilled water of the growth of a very virulent bacillus 

 on agar and. after shaking continuously for 3 days, filter. A single inocula- 

 tion is given equal to the filtrate obtained from one tube of culture. 



Effects of vaccination. 



The results obtained in man with Wright's and with Pfeiffer and Kolle's 

 vaccines will be chiefly quoted, as these are the best known methods and 

 appear to give the most satisfactory results. 



Two or three hours after inoculation tenderness develops about the site 

 of inoculation, reaches its maximum in about 12 hours, and vanishes as a 

 rule about 40 hours after inoculation. 



At the same time there is some rise of temperature accompanied by stiff- 

 ness of the back and limbs, headache, loss of appetite and nausea lasting 

 twenty-four hours or so. 



About the end of the first week the serum has acquired bactericidal, 

 agglutinating, bacteriolytic and immunizing properties, and the opsonic 

 index is raised. These newly-acquired properties rapidly increase and reach 

 their maximum on the third day after the second inoculation. 



The bactericidal and agglutinating properties persist for a long time, 

 having been demonstrated 18 months later by Bassenge and as long as 4 

 years afterwards by Harrison and others. In a person previously immunized 

 and whose serum no longer exhibits any appreciable bactericidal properties, 

 the inoculation of a very small dose of vaccine will re-create these properties 

 in a very high degree (Wassermann) : it would therefore appear desirable to 

 repeat the vaccinating inoculations at intervals in order to maintain and 

 re-enforce the immunity. 



Wright has drawn attention to a fact which is very important from the 

 point of view of prophylaxis. During the first few days less than a week 

 after inoculation there is a negative phase during which the resistance- 

 capacity of the patient to the typhoid bacillus is lowered. During this 

 period therefore vaccinated persons should not be exposed to infection, and 

 it follows that antityphoid vaccination as now practised is not permissible in 

 times of epidemic nor in endemic centres of the disease. 



Antityphoid vaccination in the human subject has been largely practised 

 in the English and German armies. The results are quite conclusive in 

 favour of vaccination. Among the vaccinated the proportion of cases is 

 markedly lower than among the unvaccinated ; moreover, the cases of 

 enteric fever which have been observed among the vaccinated have, as a 

 rule, been less severe than among the unvaccinated, and the mortality rate 

 is lower by one-half. The effects of antityphoid vaccination last for several 

 years. 



3. Besredka's method. 



The immunity conferred by the use of antityphoid serum being very 

 transitory, and the progress of vaccination with attenuated cultures very 



