128 BIOLOGY OF PNEUMOCOCCUS 



mixing with droplets of peritoneal exudates from mice previously 

 injected with pneumonic sputum loopfuls of diluted Type I, II, 

 and III agglutinating serums. Instead of spreading and fixing the 

 film, the material was immediately examined under a cover-slip. 

 The differences in the two methods are minor and the selection of 

 one or the other is a matter of personal choice. The important ob- 

 servation of Armstrong's was that an increase in the size of the 

 cocci appeared after the addition of homologous serum — the sig- 

 nificant Quellung effect first observed by Neufeld and later made 

 the basis by Neufeld and Etinger-Tulczynska 987 for their rapid 

 type-determination method. A year later, Armstrong 23 published a 

 supplemental report on the results obtained by his method. In 

 every case the type determinations were confirmed by mouse inocu- 

 lation and other methods not specified. He also reported its ap- 

 plicability to cerebrospinal fluids, pus from empyemata, aural dis- 

 charges, and exudates from various sources. 



Logan and Smeall 823 slightly changed the Armstrong modifica- 

 tion of the Sabin method, but the change was insignificant and the 

 satisfactory results the authors obtained with it might well be 

 credited to the original procedure. 



Calder 196 devised another slight modification of the Sabin tech- 

 nique. The cultures grown in Avery's medium were dried on a 

 cover-glass, stained with a drop of gentian violet solution, and 

 after the addition of diluted type serums, the preparation was ex- 

 amined as a hanging drop. 



Valentine, 1444 in 1933, introduced yet another variation of the 

 Armstrong-Logan and Smeall modification of the original Sabin 

 method. Here again, sputum and serum samples were mixed, al- 

 though in a somewhat different manner, smears made and stained 

 first with carbol-fuchsin and then carbol-thionin. The bodies of 

 the cocci, when the immune serum was homologous for the strain, 

 stained black while everything else on the slide was red, including 

 the capsule. It is difficult to discover any advantage in this tech- 

 nique over the simpler methods. 



