26 (196) Society for Experimental Biology and Medicine. 



The Negritos did better than many more advanced races. The 

 results obtained by the author are thus opposed to the view that 

 the color sense has developed within human history from a more 

 primitive type, in which only the red end of the spectrum appeared 

 as colored. 



8 (100). "The practical concentration of diphtheria anti- 

 toxin " : R. B. GIBSON. 



The methods which have been proposed for the purification or 

 concentration of antitoxins are, for the most part, peculiar and 

 tedious ways by which the whole or a portion of the globulins are 

 separated from serum or milk. Evaporation and freezing have 

 been tried, but the general use of such methods has not been con- 

 tinued. Pick states that by the isolation of his soluble or high 

 ammonium sulfate fraction, it is possible to concentrate the protec- 

 tive properties several times. Though superficially the most appli- 

 cable, Pick's method is open to certain objections. Considerable 

 quantities of antitoxin may be carried down with the nonprotective 

 fraction on one-third saturation of the serum with ammonium sul- 

 fate. Such a concentration is also not practicable. 



An artificial concentration can best be effected, for the present 

 at least, by preliminary isolation of the antitoxin globulins ; on this 

 procedure is based the plan of the following method which has 

 proved fairly successful. 



The serum is precipitated with an equal volume ot saturated 

 ammonium sulfate solution and, after reprecipitation, is extracted 

 with a solution of saturated commercial sodium chlorid. The anti- 

 toxic globulin is easily dissolved in the chlorid solution. The non- 

 soluble globulin settles to the bottom on standing. After filtering, 

 the NaCl solution of the antitoxic globulin is precipitated by the 

 addition of a half volume of saturated ammonium sulfate solution, or 

 better still, with acetic acid in the usual way. The filtered precipitate 

 is pressed as dry as possible with paper and dialyzed in parchment 

 a few hours. Its solution is then neutralized and dialyzed again 

 in running water. After two or three days' dialysis of the neutral- 

 ized solution of the protein precipitate, sterilization is accomplished 

 by double filtration through a Berkefeld filter. Before filtration, 

 sufficient sodium chlorid is added to make its proportion equal to 



