260 



INFECTION AND RESISTANCE 



lutes serum with equal parts of isotonic salt solution and heats it to 

 70 C. for 30 minutes in a water bath. To 60 c. c. of such a solution 

 he now adds 10 c. c. of ? NaOH, and continues heating for 15 to 

 20 minutes. At the end of this time he neutralizes with HC1, cools, 

 and injects 20 c. c. intraperitoneally into rabbits. (The neutraliza- 

 tion is not absolutely necessary.) Five or more injections yield a 

 serum sufficiently potent for use. 



A precipitin so produced will, according to Schmidt, react spe- 

 cifically with heated proteins, and also with protein which has been 

 solidly coagulated and brought into solution by means of N"aOH and 

 heat. It will not, however, react with normal unheated antigen. 



He tested this by coagulating horse serum by boiling for 3 hours. 

 The coagulum was washed with salt solution, dried, and powdered. 

 Tests were then made to prove that this powder was entirely in- 

 soluble in !N~aCl solution. A little of it was then treated with 10 

 c. c. of salt solution containing enough NaOH to correspond to an 

 ^ solution. The exposure was continued for 20 minutes in a water 

 bath at 60 to 70 C. Before the entire mass was dissolved the solu- 

 tion was filtered and neutralized with -^ HC1. 



The rather complicated relations described by Schmidt are easily 

 surveyed in the following protocol taken from his work : 



TABLE I 



(W. A. Schmidt, Zeitschr. f. 7mm., Vol. 13, 1912, p. 



173) 



Schmidt speaks of the "heat-alkali-precipitin" also as "alkali- 

 albuminate-precipitin." It can be produced only if the NaOH treat- 

 ment of the serum is cautiously performed. If the sodium hydroxid 

 is allowed to act too vigorously in strong concentrations or for too 

 long a time the antigen is completely destroyed, is no longer pre- 



