202 ACTIVE IMMUNIZATION 



polyvalent, i. e., composed of organisms derived from a number of 

 cases of the kind that is under consideration, or from one single 

 case, but not from the individual who is to be treated. As long 

 as we know so little of what vaccines may accomplish it is clear 

 that our clinical knowledge is not sufficient to decide such a question. 

 We can only speak theoretically, and theoretically we must admit 

 the probable existence of many strains of a given type of organism, 

 and with this the possibility of individual differences, so that upon 

 this basis autogenous vaccines would, cceteris paribus, appear to be 

 preferable to stock vaccines. But as it is frequently and in some 

 infections indeed uniformly impossible to prepare an autogenous 

 vaccine, we may be forced to use stock material in many cases. 



The preparation of the majority of vaccines is conducted as follows : 

 Cultures are made from whatever source is available, i. e., from the 

 pus of abscesses, from acne pustules, the urine, blood, sputum, etc., 

 the culture medium being chosen in accordance with the type of 

 organism that is expected, or which a preliminary examination has 

 shown to be present. If only one type is found, the vaccine is 

 made from it, while in the event of a multiple infection, or in the 

 presence of contaminating saprophytic organisms, the predominating 

 pathogenic varieties are chosen, i. e., those which are recognized as 

 being pathogenic either by direct examination or by passage through 

 an animal. 1 



Having once secured an initial supply, it is then only necessary 

 to inoculate a sufficient number of tubes or flasks of agar, or serum 

 agar, and to incubate these as usual. With organisms that furnish 

 a prolific growth, incubation for twenty-four hours is sufficient, while 

 with the more delicate organisms, such as the streptococcus and 

 pneumococcus, it is advisable to wait for forty-eight to seventy- 

 two hours. At the expiration of this time a small amount of sterile 

 saline solution (10 c.c. to an ordinary agar slant) is poured into the 

 first tube and the growth gently scraped off with a platinum loop. 

 The emulsion is then poured into the next, from this into the follow- 

 ing, and so on, according to the number of tubes or the quantity of 

 vaccine which is to be prepared. 



1 In this connection I cannot condemn too strongly the use of some of the 

 so-called polyvalent and mixed vaccines which have been recently placed upon 

 the market with the most extravagant claims for their efficacy in the absence 

 of any proof of their value. 



