PLATE XXIV 



FIG. i. DIPLOCOCCUS PXEUMONL-E. 



Culture on Loffler's blood-scrum, of twenty-four hours' age, incubated at 37 C. 



Stained by Gram's method. The cover-glares having been prepared in the usual way, 

 are immersed ina watch-glass of aniline gentian violet for ten minutes, passed through water, 

 and then placed in Gram's iodine solution for five minutes, after which they are washed in 

 alcohol until no further colour comes away ; they are then placed on edge to dry, and finally 

 mounted in xylol balsam. 



The cocci occur singly and in pairs, but mostly grouped in rows of varying length. In the 

 particular strain shown (which was isolated by Dr. J. W. Wash bourn and Dr. J. Eyre, 

 and found highly virulent when tested upon animals' the chain formation is unusually pro- 

 nounced, the organism being a streptococcal variant. 



Considerably longer chains than the longest depicted were present. The cocci composing 

 the chains are actively subdividing, as evidenced by the flattened pairs of which they so 

 largely consist. Here and there unusually large elements occur in which sub-division has 

 not yet taken place. 



In pure cultures the organism is unprovided with the capsule which it presents when 

 studied in the sputum and pulmonary tissue in cases of acute pneumonia. 



FIG. 2. 



A preparation of the heart-blood of a rabbit expejimentally infected with the foregoing 

 strain of diplococcus pneumoniae by intra-peritoneal injection. All the organisms, whether 

 single cocci or pairs, are surrounded with a thick capsule. The specimen was dyed with 

 the following modification of dahlia stain devised by Dr. A. MacConkey : Dahlia, '5 grms. ; 

 methyl green (oo crystal), 1*5 grms.; saturated alcoholic solution of fuchsine, 10 c.cm. ; 

 distilled water to 200 c.cm. 



The dahlia and methyl green are rubbed up in a mortar with part of the water until 

 dissolved, the fuchsine is then added, and, finally, the rest of the water. The cover-glass, 

 after the dye is placed upon it, is held over a low flame until the steam rises, placed asicl- 

 for five minutes, washed, allowed to dry, and, finally, mounted in xylol balsam. 



The appearance of the capsule under the conditions of the experiment and in the human 

 tissues possibly marks a defensive formation on the part of the bacterium to protect it against 

 the action of the cells and body fluids (Louis Jenner). 



FIG. 3.-TETANUS BACILLUS. 



Culture in glucose broth, grown anaerobically at 37 C. ; stained with gentian violet. 



Slender rods and simple filaments. Most of the rods have sporulated, the spore being of 

 spherical form and situated at one end of the rod which, in consequence, acquires the 

 appearance of a drum-stick. Branching filaments may be met with, as in the case of the 

 tubercle bacillus. 



