114 THE POSSIBLE OCCURRENCE OF [CH. vm 



The oft mooted question of the relationship of the meningo- 

 coccus to the pneumococcus is prompted by clinical rather than 

 by bacteriological evidence. Pneumococcal meningitis, like all 

 pneumococcal infections, is characterised by certain features 

 which are also observed in meningococcal meningitis (Preble), 

 namely an acute onset, a polymorphonuclear leucocytosis, 

 a diminution in the chlorides in the urine, and herpes. In the 

 second place, certain complications are common to both, namely 

 endocarditis, pericarditis, arthritis and otitis media. In the 

 third place, Preble observes that there is an extraordinary 

 similarity in the seasonal distribution of the two diseases. 

 On these grounds he suggests that the meningococcus is a 

 variant of the pneumococcus. Certain differences between the 

 two diseases exist. The petechial eruptions which formerly 

 gave a name to one disease are rare in the other, but this haem- 

 orrhagic tendency is altogether absent in some epidemics of 

 "meningococcal" meningitis. Again, " meningococcal" menin- 

 gitis is a disease more especially of childhood and frequently 

 ends in recovery; "pneumococcal" meningitis is a disease 

 more commonly of adult life and is invariably fatal. The 

 differences in age incidence and mortality are however com- 

 patible with the view that the causal organism is the same 

 but of different virulence. 



Finally, the sporadic nature of meningococcal meningitis, 

 which is difficult to'explain if one admits the meningococcus 

 to be an independent organism, ceases to be so if one assumes 

 it to be a modified form of the ubiquitous pneumococcus. 



It may be argued that, although each of the several differ- 

 ences in character which distinguish the organisms we have 

 been comparing, when considered by itself, may appear* trivial 

 and may prove to be variable, nevertheless all these differences, 

 if taken together and viewed as a whole, represent a degree 

 of divergence in type which cannot be so lightly dismissed. 

 A series of surmises, no matter how credible these may be 

 made to appear, does not constitute a proof. It is in our 

 power to prove, however, that in other cases differences no 

 less diverse in character and no less marked in degree, differ- 

 ences moreover which, taken together and viewed as a whole, 



