566 BIOLOGY OF PNEUMOCOCCUS 



unit of antibody was defined as the smallest amount of serum that 

 would protect rabbits under the conditions of the test. High viru- 

 lence of the cultures for rabbits was maintained by special meth- 

 ods. Washbourn also tested the therapeutic action of serum in rab- 

 bits and gauged the dosage on the basis of units of antibody. Eyre 

 and Washbourn 374 reported further experiments on standardiza- 

 tion, employing mice and administering the mixtures subcutane- 

 ously. The authors stated that there was no relation between pro- 

 tection, agglutination, and bactericidal action of the serums — an 

 observation that must be discounted in view of evidence obtained 

 by more recent investigators. In a later publication, Eyre and 

 Washbourn 377 announced the method adopted by them for stand- 

 ardizing antipneumococcic serum, which depended upon determin- 

 ing the protective power of 1.0 cubic centimeter of serum in terms 

 of the number of fatal doses of highly virulent pneumococci in- 

 jected. The serum was administered intravenously to rabbits and 

 was followed immediately by an intraperitoneal inoculation of cul- 

 ture, the minimal lethal dose of which was determined by injecting 

 various dilutions of the culture into control rabbits. 



In testing the protective value of various serums, Romer 

 (1902) 1155 made simultaneous injections of culture and of serum, 

 using both mice and rabbits and, in 1905, 1156 he made a further 

 report of his technique in which a series of mice were inoculated 

 subcutaneously with decreasing doses of serum. After twelve to 

 seventeen hours the test animals and the controls were injected 

 with 10 to 100 lethal doses of culture. For the purpose of inter- 

 preting results, Romer termed a serum of which 0.01 cubic centi- 

 meter protected animals a "simple serum" and assumed that one 

 cubic centimeter of simple serum constituted one "immunizing 

 unit." If the protective dose was found to be one milligram, the se- 

 rum was designated as "10 normal." It is difficult to compare the 

 definitions of units as described by Washbourn and by Romer, but 

 their contributions demonstrated the feasibility of standardizing 

 antipneumococcic serum by the use of animals. 



