24 * ACTIVE IMMUNIZATION. 



It is now clear that immunization with living bacteria can 



Example on ^ ^ e undertaken if the latter belong to the class of half- 



of Active parasites. Pure parasites are excluded from this method. 



Immunization As an example of such procedure can be given the immu- 



with Living nization of a guinea-pig by intraperitoneal injections with 



acilh. li v i n g typhoid bacilli. Preliminary to this, the virulence 



of the typhoid culture must be ascertained. 



a. Preliminary test to titrate the virulence of the typhoid culture. 



1. Guinea-pig i./I. 1909 1/20 loopful of typhoid culture intraperitoneal. 



2./I. active. 



8./I. alive. 



2. Guinea-pig i./I. 1909 i/io loopful of typhoid culture intraperitoneal. 



2./I. active. 



8./I. alive. 



3. Guinea-pig i./I. 1909 1/8 loopful of typhoid culture intraperitoneal. 



2. /I. slightly sick, does not eat. 



3. /I. active. 



8./I. alive. 



4. Guinea-pig i./I. 1909 1/6 loopful of typhoid culture intraperitoneal. 



2. /I. sick, does not eat, hair raised. 



3./I. still sick. 



4./I. more active. 



8./I. alive. 



5. Guinea-pig i./I. 1909 1/5 loopful of typhoid culture intraperitoneal. 



2. /I. sick, does not eat, hair raised. 



3./I. very weak, when placed on side remains so. 



4-/I. t ' 



6. Guinea-pig i./I. 1909 1/6 loopful of typhoid culture intraperitoneal. 



2./I. ' f 



From this experiment it becomes evident that the letal dose of this particular strain 

 of typhoid culture is 1/4 to 1/5 of a loopful for guinea-pigs by intraperitoneal injection. 

 Immunization therefore must be started with a smaller dose e. g., i/io of a loopful. 



b. Immunization. 



1. Guinea-pig 8./I. 1909 i/io loopful of typhoid culture intraperitoneal. 



i6./I. 1/8 loopful of typhoid culture intraperitoneal. 



22. /I. 1/4 loopful of typhoid culture intraperitoneal. 



Animal remains active and healthy. 

 30./I. I loopful of typhoid culture intraperitoneal. 



5./II. 2 loopfuls of typhoid culture intraperitoneal. 



Animal remains active and healthy. 



2. Guinea-pig 8./I. 1909 i/io loopful of typhoid culture intraperitoneal. 



i6./I. 1/4 loopful of typhoid culture intraperitoneal. 



Animal remains active and healthy. 



3. Guinea-pig 8./I. 1909 i/io loopful of typhoid culture intraperitoneal. 



i6./I. 2 loopfuls of typhoid culture intraperitoneal. 



I7-/I. animal is sick and does not eat. 



i8./I. animal is very weak. 



i 9 ./L t 



