434 PROTEIN POISONS 



sulphate solution, then dissolved in water, equal in amount 

 to the original leukocyte extract, and then precipitated again 

 with ammonium sulphate before dissolving in saturated 

 sodium chloride solution, but such a procedure is unneces- 

 sary when the extract has been previously filtered through a 

 Berkefeld, inasmuch, as previously shown, four-fifths of the 

 albumin is removed at this time. 



Again, it was my custom to filter after dissolving in 

 saturated sodium chloride solution, but this has been 

 abandoned because of the fact that if insufficient saturated 

 sodium chloride is used, much globulin may be retained 

 by the filter, and, inasmuch as the excess of ammonium 

 sulphate is all that is desired to be rid of, both time and 

 material can be saved by not filtering. The saturated 

 sodium chloride solution is always filtered before using. 



Again, it was my custom to dialyze through parchment 

 paper after collecting the precipitate thrown down by 0.25 

 per cent, acetic acid, but repeated experiment has shown 

 that the percentage of acetate when the globulins are 

 dissolved in the proportion of 1 mg. to 1 c.c. of normal 

 saline is so small as to be of no moment, and it is much 

 preferable to have a solution of normal saline than one of 

 sterile water for injection in the patient. 



It should be added that precipitation is aided by allowing 

 hot water to pass over the outside of the flask until the 

 temperature of the contained fluid is about 30 C. 



The following experiment has been repeated many times, 

 so that the possibility of 'error is slight. 



(a) 10 c.c. of soluble globulins from sensitized leukocyte 

 extract plus 5 c.c. normal saline were incubated one hour, 

 and 10 c.c. of this injected intravenously into a small rabbit. 

 There was no change in the animal. 



(6) 10 c.c. of soluble globulins from sensitized leukocyte 

 extract plus 5 c.c. of 2 per cent, cancer-cell emulsion were 

 incubated one hour and then injected intravenously into 

 a moderate-sized rabbit. The rabbit died in one-half 

 minute. 



From the above it can be seen that the specific ferment 



