BACILLI OF THE COLON-TYPHOID-DYSENTERY GROUP 683 



and mouse inoculated to insure sterility. For immunization 3 to 4 

 doses are given ranging in quantity from 500 million to one billion at 

 seven- to ten-day intervals. The protection probably lasts about two 

 years, though this is not certain. 



Another point of importance in this connection has recently been 

 raised by Metchnikoff and Besredka. 120 They vaccinated chimpanzees 

 with typhoid bacilli and found that when emulsions of the clear bac- 

 teria were used, protection was only slight. Better results were obtained 

 that is, apparently complete protection within eight to ten days 

 when living sensitized bacteria were injected (bacteria which had been 

 exposed to the action of inactivated immune serum.) Broughton has 

 applied this method to human beings. Gay 76 has also prepared a sen- 

 sitized dead typhoid vaccine which he has used in a considerable 

 number of cases. It will take some time, however, before a statistical 

 estimation of the superiority of this method over the older vaccination 

 with dead bacteria will be possible. 



Gay 76 sensitizes his bacilli with strong immune serum, precipitates 

 with alcohol, dries and grinds them into powder, and uses weighed 

 amounts of the powder. 



During recent years in France another form of vaccine has been 

 used which has advantages which lead to its general adoption, if its im- 

 munizing value can be successfully proven. This is the so-called "lipo- 

 vaccine." It consists of typhoid cultures grown on agar, taken up in salt 

 solution, the sediment partially dried, and then shaken up with olive oil, 

 the formula for which is not available. It can also be produced by grind- 

 ing up the typhoid sediment with lanolin and shaking up this well-ground 

 paste with sterile olive oil. Great difficulty has been encountered in the 

 sterilization of this vaccine, a matter which still needs much investiga- 

 tion. The vaccine has the advantage of giving much diminished reac- 

 tions, and it is claimed that three times the amounts given in the 

 ordinary saline suspensions can be given without serious discomfort to 

 the patient. There is probably slow absorption of this vaccine and it is 

 claimed that a single dose, because of the slow absorption of the organ- 

 isms, may be sufficient to vaccinate. 



During the recent war, typhoid vaccination has thoroughly justified 

 itself. We are not in possession at the present writing, of consolidated 

 reports of all the European Armies, but the Surgeon General's report for 

 the United States Army, published in 1919, shows the magnificent results 

 obtained by vaccination in American troops. During the pre-vaccination 



120 Metchnikoff and Besredka, Am. dc Tinst. Past., 1911. 



