440 Diphtheria 



method of testing, but as toxic bouillons contain varying quantities 

 of toxoids it may equal anywhere from fifty to one hundred and fifty 

 times that dose. 



The test dose of toxic bouillon, having been determined, remains 

 invariable throughout the test as before, the serum to be tested for 

 comparison with the standard being modified. The calculation is, 

 however, different because the guinea-pig is receiving, not ten times, 

 but more nearly one hundred times the least fatal dose, and the quan- 

 tity of the antitoxic serum that preserves life beyond the fourth day 

 is itself the unit. 



Example: The sample of serum issued as the standard contains 17 

 units per cubic centimeter. Serum 1 c.c. + water 16 c.c. = 1 c.c. 

 is the unit. 1 c.c. of the dilution containing one antitoxic unit is 

 mixed with 0.01, 0.025, 0.05, 0.075, 0.1 c.c. of the toxic bouillon. All 

 the animals receiving less than 0.1 c.c. live. A new series is started, 

 and the guinea-pigs all weighing exactly 250 grams receive 1 unit of 

 the antitoxin plus toxic bouillon 0.08, 0.09, 0.095, 0.097, 0.1, 0.11, 

 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 0.1, 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 0.1 c.c. plus varying quantities of the 

 serum T , -g 7 , , etc. All live except those receiving less than 

 ffa, 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 H6chst-on-the-Main, but at 

 present the United States Public Health and Marine Hospital Service 

 has undertaken the control of the manufacture of therapeutic serums 

 and kindred products in the United States, issuing licenses to those 

 engaged in legitimate manufacture, and also furnishing a standard 

 serum, similar to that of Ehrlich, from their own laboratory in Wash- 

 ington. 



A full description of "The Immunity Unit for Standardizing Diph- 

 theria Antitoxin," by M. |. Rosenau, Director of the Hygienic Labor- 

 atory, 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 methods of concentration have been suggested, such as the 

 partial evaporation of the serum in -vacua, but none has yet proved sat- 

 isfactory. Bujwid* and H. C. Ernst f 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 yel- 

 lowish layer being about three times that of the original serum, the 

 upper layer consisting chiefly of water. 



Administration. Ehrlich asserts that a dose of 500 units 

 is valueless for the treatment of diphtheria, 2000 units being 



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

 10 and 11, p. 287. 



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

 137. 



