40 MICRO-ORGANISMS AND DISEASE. [CHAP. 



material. This pellicle is composed of zoogloea, and after 

 some time bits of it, or the whole, sink to the bottom if the 

 medium is fluid. Micrococci that thus form pellicles are pre- 

 eminently aerobic (Pasteur), i.e. require a great deal of free 

 oxygen, which they receive from the air to which they are 

 exposed on the surface of the nourishing material. Other 

 species do not require free oxygen (anaerobic, Pasteur), and 

 therefore grow well in the depth and do not form a superficial 

 pellicle. There is a marked distinction in this respect between 

 different species. The micrococci occurring in connexion with 

 disease are anaerobic. 



When cultivated in the incubator in suitable fluid nourish- 

 ing material, they produce after a day or two general 

 turbidity. 



Micrococci may be divided, according to their chemical and 

 physiological function, into : (a) septic, (6) zymogenic, 1 (c) 

 chromogenic, and (d) pathogenic micrococci. 



(a) The septic micrococci are micrococci that occur with other 

 septic bacteria, wherever there is decomposition of organic 

 matter in solids or in fluids. There exists a large number of 

 species of such micrococci, differing from one another in size 

 and mode of growth. They are widely distributed in the air, 

 and contamination by air is often followed by the appearance, 

 of micrococci. They also occur in the body of man and 

 animals wherever there is dead tissue, in which they grow 

 well and copiously. Of this kind are the micrococci found in 

 ordinary pus (Ogston), in the normal oral cavity (on the filiform 

 papillae of the tongue and on the mucous membrane), in the 

 bronchial secretion in ordinary catarrhal exudations (nasal 

 cavity, bronchi, &c.), on the free surface of intestinal and 

 other ulcerations, and in the cavity of the small and large 

 intestine. 



(b) Zymogenic micrococci are micrococci associated with de- 

 finite chemical processes, (a) Micrococcus urese, causing the 

 ammonical fermentation of urine (aerobic, Pasteur), occurs 

 singly, as dumb-bells or chains, and as zoogloea. (/3) The 

 micro-coccus of the mucoid wine fermentation produces 

 (Pasteur) a peculiar mucoid change in wine and beer, and 

 occurs chiefly in chains, (y) The micrococcus causing phos- 

 phorescence in putrid meat and fish (Pfliiger) forms chiefly 

 zooglcea (aerobic). 



1 I adopt this term from Fliigge : Fermente und Mlkroparasitcn, Leipzig, 1883. 



