698 ACTIVE IMMUNIZATION 



paration of plague vaccine, and removing the growths with sufficient 

 salt solution so that 1 c.c. shall contain one loopful (4 mm.) of organisms 

 (2 mg.). The emulsion is then shaken to break up clumps, heated to 

 60 C. for from one-half to one hour, cultured to determine sterility, and 

 preserved with 0.5 per cent, phenol. 



Strong has proposed the use of the products obtained by "autolytic 

 digestion" of the organism, i. e. } by incubating an emulsion of them in 

 sterile water, in which they break up spontaneously. Twenty-four-hour 

 agar cultures are removed with sterile water, placed in a sterile flask, 

 and kept at a temperature of 60 C. for twenty-four hours. The mixture 

 is then put aside in the incubator for from two to five days. The best 

 results are obtained apparently after five days' autolytic digestion. 

 After such digestion the emulsion is filtered through a Reichel filter. 

 The fluid thus obtained must, of course, be examined for sterility and 

 carefully standardized before being used as a human vaccine. 



Dosage. Kolle's vaccine is given subcutaneously in two injections 

 about a week apart 1 c.c. the first time and 2 c.c. the second time. 



Haffkine's vaccines are given in the same manner at an interval of 

 five days. 



The local effects are usually marked by more or less pain and edema, 

 which subside in forty-eight hours. The constitutional effects are not 

 infrequently severe, being marked by malaise, fever (100 101 F.), 

 nausea and vomiting, followed the next day in about 10 per cent, of 

 persons by transient diarrhea. Usually all symptoms have disappeared 

 within seventy-two hours. 



Results. Haffkine's prophylactic vaccine has yielded favorable 

 results in India. Powell reports 198 cases of cholera among 6549 non- 

 immunized persons, with a total mortality of 124. Of 5778 inoculated 

 persons, there were 27 cases, with 14 deaths. Much better results were 

 obtained with Kolle's vaccine, and it is now generally used in preference 

 to the Haffkine vaccines. 



Murata, during an epidemic in Japan in 1902, vaccinated 77,907 

 persons. Of these, 47, or 0.06 per cent., developed cholera, and 20, 

 or 0.02 per cent., died. Of 825,287 uninoculated persons, 1152, or 0.13 

 per cent., died. During a recent epidemic in Russia Franschetti inocu- 

 lated 11,178 persons. Of these, 8 contracted cholera and 1 died. In 

 St. Petersburg, during 1907-08, 30,000 persons were inoculated. Of 

 these, 12 developed cholera and 4 died. Of 10,000 uninoculated per- 

 sons, 68 contracted the disease. 



It appears justifiable, therefore, to conclude that inoculation confers 



