62 MEDICAL BACTERIOLOGY 



In doubtful cases differentiation of streptococci and pneumococci is difficult 

 because intermediate forms not only vary from classic streptococci and pneu- 

 mococci in morphology, but also in cultural characteristics, effects on rabbits, 

 and behavior when mixed with agglutinins. 



SERUM AND VACCINE THERAPY 



A small percentage of cases of streptococci infection is greatly benefited by 

 serum treatment, the condition being improved to a degree unattainable by 

 other measures, but the majority is not influenced, and taken as a whole, serum 

 treatment of streptococcus infections is still unsatisfactory. 



The same is true of vaccine treatment of acute streptococcus infections, but 

 in the treatment of chronic or recurrent streptococcus infections and the sequelae 

 of erysipelas, autogenous vaccines have a distinct value, and it is always ad- 

 visable to employ them. 



The extensive studies of streptococci and pneumococci executed in recent 

 years by Rosenow and published in the Journal of the American Medical Asso- 

 ciation and other American journals of medicine, should be carefully read by 

 advanced students. Among other things clearly disclosed is the fact that in 

 some (possibly many) species of bacteria there are strains that will not grow in 

 culture media under ordinary aerobic or anaerobic conditions; organisms that 

 only grow in a certian oxygen concentration, the limits of which are narrow. 



To insure growth of such organisms extra long test-tubes are filled with solid 

 media nearly to the top. Either shake or stab cultures are made so as to dis- 

 tribute the plant from top to bottom of the tube. Under such conditions growth 

 generally occurs in a zone % to i inch in depth; the medium above and below 

 appearing sterile. Such zones of growth may, with different organisms, develop 

 at any level from near the bottom to near the top of the tube. 



The proper oxygen supply or tension may be provided for such sensitive 

 strains so as to induce growth by connecting the tube planted with streptococci 

 to a tube planted with bacillus subtilis, with a small hose, in such a way that 

 the cultures do not mix. 



