172 APPLIED IMMUNOLOGY 



free of bacilli, as determined microscopically, cultur- 

 ally and by animal inoculation. One cubic centimetre 

 of this extract represents one-half gramme of the 

 bacillary mass. One-half per cent, phenol is added as 

 a preservative. 



Tuherculinum Purum {" T, P"), — According to 

 " New and Non-official Remedies," this Russian 

 tuberculin is " the purified filtered extract of human 

 tubercle bacilli in 50 per cent, glycerin, prepared in 

 the same way as in Koch's old tuberculin, but subse- 

 quently treated with alcohol, ether, chloroform and 

 xylol in order to remove deutero-albumoses." These 

 toxalbumins and glycerin-soluble by-products of the 

 culture medium are held responsible for a certain 

 amount of the toxic reaction noted in using old tuber- 

 culin and their elimination has resulted in this so- 

 called purified tuberculin. 



Technic of Making Dilutions 



Many pharmaceutical firms to-day market tuber- 

 culins in serial dilutions most convenient for immediate 

 use. However, if it be desirable or necessary to em- 

 ploy stock preparations, the following technic may be 

 found useful : 



Pipettes. — (a) One-tenth c.c. pipette, graduated 

 in hundredths, is most economical of stock in making 

 tuberculin dilutions. 



