xvi BIOLOGY OF PNEUMOCOCCUS 



tributed to recovery by instituting supportive measures until the 

 natural capabilities of living tissue have repaired the injuries in- 

 flicted by the invading microorganisms. 



The bacteriologist has persisted in the pursuit of information, 

 and as a result the positive identification, the growth needs, and 

 much of the physiological behavior of Pneumococcus are now com- 

 mon knowledge. The immunologist, by serum reactions, has found 

 that pneumococci are not all alike; that they may become de- 

 graded and even transmuted into strange forms, and that on this 

 degradation or exaltation depend certain vital processes within 

 the cell related to virulence and the morbid effects produced in the 

 animal economy. With this information he has devised ways of 

 identifying types among the species, and of using the cocci for 

 his own purposes. 



In time the chemist joined forces with his colleagues in the field 

 of medical science, and as a result of their combined efforts the 

 answer has been found to some of the riddles which the bacteri- 

 ologist alone could not solve. Breaking down Pneumococcus into 

 its component parts, the chemist found the expected protein, and 

 then discovered the new sugars which have so altered our ideas 

 about pneumococci in general, and which are bringing a solution 

 to the cryptic working of the immunological mechanism. 



The chemist, laboring with the bacteriologist and immunologist, 

 has given us a new conception of the significance of chemical con- 

 stitution and molecular arrangement in determining the power of 

 proteins and of carbohydrates, either alone or combined, to call 

 into activity those reactions which spell the fate of the infected 

 host or the fate, not only of Pneumococcus, but of other bacteria 

 and even of non-living alien substances that gain entrance to the 

 animal body. New biological principles have been disclosed, ex- 

 plaining many of the functions of the living bacterial cell amidst 

 both natural and artificial surroundings and opening fresh and 

 inviting paths of investigation. 



The study of the members of this small group of microorganisms 



