BACTERIOLYSINS AND H&MOLYSINS 121 



done by making the dilution n per cent or 9 per 

 cent as may be necessary. It is not well to use corflh 

 plement which must be made up in dilutions stronger 

 than 8 per cent. Complement more than twenty- 

 four hours old must not be used. 



A satisfactory method of preserving complement 

 is to add to each 5 cc. of the undiluted complement 

 .4 gram of dry C. P. sodium chloride. It then may 

 be kept one week in the refrigerator and diluted 

 with nine times its amount of distilled water before 

 using. 



Antigen. At least 100 cc. of absolute ethyl 

 alcohol is placed in a tightly stoppered bottle and 

 to this is added the hearts of normal guinea pigs 

 as the pigs are killed from day to day for the prep- 

 aration of complement, until the proportion of one 

 heart to each 5 cc. of alcohol has been reached. The 

 hearts are prepared as follows: Freed from fat and 

 cut into halves, thoroughly washed in tap water and 

 dried on a cloth free from lint, then placed in 95 

 per cent alcohol for about five minutes in order to 

 remove any traces of water remaining, again dried, 

 cut into small pieces and added to the stock bottle. 

 The smaller the amount of water which finds its 

 way into the stock bottle the better will be the anti- 

 gen. The bottle is placed in the ice chest, shaken 

 from time to time and at the end of about one 

 month is ready for use. If heat is applied or if the 

 bottle is kept at incubator temperature, a different 



