72 RELATIONSHIPS OF THE COCCACE^ 



gation. Serum reactions, in spite of their variability, 

 throw considerable light on the mutual relationships of 

 the parasitic cocci; and the numerous investigations 

 which have been carried out by students of the diplococci 

 and the streptococci will be discussed in Chapters V and 

 VII. In some groups, notably among the white and 

 orange staphylococci of the skin, further comparative 

 study of agglutinative reactions in relation to various bio- 

 chemical powers should prove of value. 



Among other measures of bacterial activity the test 

 for the liquefaction of starch is one which it seems 

 logical to include with those which show the relation 

 of an organism to gelatin and the sugars; and we, 

 therefore, made some experiments with the starch media 

 introduced by Smith (1905). It appeared that certain 

 cocci did exert an amylolytic action; and the further 

 study of this character would probably prove of con- 

 siderable interest. 



Those characters which we finally chose as most likely 

 to throw light on the systematic relationships of the 

 Coccaceas are as follows: (Each of the tests was applied 

 under comparable conditions to the series of 500 cocci 

 at our disposal.) 



DIAGNOSTIC TESTS USED FOR STATISTICAL STUDY OF 

 THE COCCI. 



i. Habitat. Recorded as 1 (diseased conditions); 

 2 (normal body); 3 (water); 4 (earth); or 5 (air). The 

 significance of these various habitats has been more 



