Pfeiffer's Bacilli (127) — Different Kinds of Bacteria as Growth-Pro- 

 moting Microbes (131) — Can more than one Growth-Promoting Sub- 

 stance be Demonstrated? (134)). 



Growth on Blood Agar 137 



Appearance of the Colonies 139 



Account of the Macroscopic Morphology 144 



Microscopic Morphology 145 



(The strongly developed Polymorphism (145) — Vain Attempt at a de- 

 finite Morphological Classification (146) — The Spherical Bodies and 

 their Characteristic Staining (147) — Morphology in a Fluid Medium. 

 Motility? (150) — Connection between Macroscopic and Microscopic 

 Morphology (150)). 



Relation to Oxygen 151 



Relation to the Reaction of the Medium 152 



Minimum Temperature for Growth 153 



Resistance against Heating, Drying and Keeping 158 



Fermentation Tests 161 



Investigation of Proteolytic Power 164 



Indol Formation 164 



(Sharp Division into Indol-Producers and Non-Indol Producers, Largely 

 Independent of Long-Continued Cultivation and Wide Variations in the 

 Constitution of the Medium). 



Agglutination 1 76 



(General Technique; Investigation of the Accuracy of a Simple Nephel- 

 ometric Method and Indicaiion of the Limits of its Applicability (176) 

 — Demonstration of Sharply-Defined Differences in Agglutination amongst 

 Different Strains of Pfeiffer's Bacillus (181) -^- -Systematic Examination 

 of the Conditions Governing Agglutination (184) — Special Study of 

 Strains from Influenzal Pneumonia (188) — Various Agglutinin Absorp- 

 tion Experiments (191) — Cerebro-spinal Strains (192) — Miscellany 

 (192)). 



Complement Fixation 194 



Summary of the Characters of Pfeiffer's Bacilli 195 



(Enumeration of the various Characteristics (196) — Investigation of 

 Correlation between Indol Formation and Agglutination (198) — Other 

 Correlations (200) — „Mutations" (203)). 



IV. Comparison of Pfeiffer's Bacillus with Other 

 »Haemoglobinophilic Bacteria«. 



1. Hacmolytic, Haemoglobinophilic Bacilli 205 



2. Bordei's Whooping-cough Bacillus 209 



3. Bacillus haemoglobinophilus canis 214 



Symbiosis Experiments as a Means of Classification 217 



The Circumscribing "and Grouping of Haemoglobinophilic Bacteria 218 



(Which Bacteria should be Included? What Species are Known in this 

 Group?). 



