130 Immunity 



A new series is started, and the guinea-pigs all weighing exactly 250 grams, 

 receive i unit of the antitoxin plus toxic bouillon 0.08, 0.09, 0.095, -97, o- 1 ? 

 o.i i, 0.12, etc. It is found that all receiving more than 0.097 die in four days, 

 but that the animal receiving that dose, though very ill, lives longer. The 

 test dose may then be assumed to be o.i, or it may be calculated more closely 

 if desired. 



To test the serum itself, guinea-pigs weighing exactly 250 grams are now 

 all given toxic bouillon o.i cc.plus varying quantities of the serum 3^oo> Moo* 

 Moo> etc - All live except those receiving less than ^oo> which die about or on 

 the fourth day. The" serum can then be assumed to have 400 units per cubic 

 centimeter unless it be desired to test more closely. 



Standard test serums for making tests of antitoxic serums by the 

 Ehrlich method were first shipped at small expense from the Kaiser- 

 liches Institut fur Serum-Therapie at Hochst-on-the-Main. At 

 present the Hygienic Laboratory of the United States Public Health 

 Service has legal control of the manufacture of therapeutic 

 serums and kindred products in the United States, issuing licenses 

 to those engaged in legitimate manufacture, and furnishing a 

 standard test serum, similar to that of Ehrlich, to those entitled to 

 receive it. 



A full description of "The Immunity Unit for Standardizing 

 Diphtheria Antitoxin," by M. J. Rosenau, Director of the Hygienic 

 Laboratory, can be found in Bulletin No. 21 of the U. S. Public 

 Health and Marine Hospital Service, Washington, 1905. 



As the quantity to be injected at each dose diminishes according 

 to the number of units per cubic centimeter the serum contains, it 

 is of the highest importance that therapeutic serums be as strong 

 as possible. Various t methods of concentration have been sug- 

 gested. Bujwid* and H. C. Ernstf found that when an antitoxic 

 serum is frozen and then thawed, it separates into two layers, the 

 upper stratum watery, the lower yellowish, the antitoxic value of 

 the yellowish layer being about three times that of the original 

 serum, the upper layer consisting chiefly of water. 



The most satisfactory method of securing a useful concentration 

 is by the employment of the globulin precipitation as recommended 

 by Gibson, % which is briefly as follows: The diluted citrated plasma 

 is precipitated with an equal volume of saturated ammonium sul- 

 phate solution and the antitoxic proteins separated by extracting 

 the precipitate with saturated sodium chloride solution. The soluble 

 antitoxic proteins are then reprecipitated from the saturated sodium 

 chloride solution with acetic acid. This filtered precipitate is then 

 partially dried between filter-papers and dialyzed in running water. 

 This yields a final product which when dried in vacuo is readily solu- 

 ble in salt solution and is free from many of the offensive substances 

 in the horse serum. Steinhardt and Bauzhaf found that the thera- 



*"Centralbl. f. Bakt. u. Parasitenk.," Sept., 1897, Bd. xxn, Nos. 10 and n, 

 p. 287. 



" Jour. Boston Soc. of Med. Sci.," May, 1898, vol. n, No. 8, p. 137. 



j "Jour. Biol. Chem.," i, p. 161; in, p. 253. 



"Jour. Infectious Diseases," March, 1908, vol. n, pp. 202 and 264. 



