484 BIOLOGY OF PNEUMOCOCCUS 



appeared to render the individual more susceptible to infection. 

 Lister, 816 however, found that 40 billion organisms could be in- 

 jected into man without eliciting any but very slight reactions. In 

 Ferguson's 436 experimental studies on man, 150 million organisms 

 each of Types I, II, and III were injected subcutaneously at 

 weekly intervals. Barach's 75 studies were carried out with doses of 

 200 million or more cocci at each injection. Duckwall 339 adminis- 

 tered doses as small as 500 organisms at the first injection, in- 

 creasing the amount to only 1,000 cocci on two subsequent occa- 

 sions. In the study made by McCoy, Hasseltine, Wadsworth, and 

 Kirkbride, 875 the lipovaccine used contained approximately 10 

 billion organisms of Types I, II, and III. Howell 661 standardized 

 his preparation on the basis of dried pneumococcal protein and 

 found that one cubic centimeter of vaccine containing 0.83 milli- 

 gram of protein was a satisfactory dose. The circulars of direc- 

 tions accompanying the pneumococcal vaccines supplied by some 

 of the commercial laboratories usually recommend the initial in- 

 jection, in the case of a preparation containing pneumococci of 

 the first three types only, of an amount representing 4,500 million 

 organisms. For second and third doses the number is increased to 

 9,000 million pneumococci. In the case of vaccines consisting of 

 pneumococci mixed with other bacteria of respiratory origin, the 

 first dose represents 50 million pneumococci combined with 75 mil- 

 lion for the second, third, and fourth injections. It appears, there- 

 fore, that pneumococcal vaccines may be safely administered within 

 a wide range of dosage. 



SPECIAL CONSTITUENTS OF PNEUMOCOCCUS 



In the chapter on antigenicity, the immunizing action of certain 

 isolated components of the pneumococcal cell was described. It 

 may be remembered that Francis and Tillett 478 and Finland and 

 Sutliff 448 " 9 succeeded in inducing the development of specific anti- 

 bodies in man by the intradermal injection of soluble specific sub- 

 stance. Francis, 474 by injecting two groups of normal human be- 



