PNEUMONIA 145 



1 c.c. or more of a twenty-four-hour bouillon culture, while 

 0.0000001 of this amount of the other kills in the same time. 

 The virulence may be intensified by repeated passage through animals, 

 but there is great difference in the degree with which different strains 

 hold their virulence. Some of high power rapidly lose from gen- 

 eration to generation, while others remain fairly steadfast through 

 many successive generations. The difference between strains of low 

 and high virulence seems to be in rate of multiplication. Two guinea- 

 pigs are treated at the same time with the two strains mentioned 

 above. The size of one dose is 0.0000001 that of the other, 

 and still the animals die at the same time and the growth in one is 

 found after death to be as great as that in the other. It seems from 

 this that the more virulent strain has multiplied much more rapidly 

 than the other. Moreover, when large amounts of the cellular sub- 

 stance of both are obtained and split up chemically, the yield of poison 

 by the two, per gram, is the same. This certainly is strong evidence 

 that difference in virulence is determined by rate of growth. 



While the pneumococcus is quite labile in structure, under certain 

 conditions, it easily undergoes autolysis and is destroyed quickly by dis- 

 infectants. Samples of sputum have been found to retain virulent 

 cocci for months. All sputum should be burned or otherwise destroyed. 

 Floors and sidewalks are not proper receptacles for expectoration from 

 either the well or the sick. 



It is a matter of scientific interest that bile not only destroys but 

 dissolves living, virulent pneumococci. On dead and non-virulent 

 cultures bile has no such action. This solvent effect has been found 

 to be due to the bile acids. Since most other pathogenic bacteria 

 easily multiply in undiluted bile, this effect on pneumococci is striking 

 and interesting, although it is not known to be of any practical 

 importance. 



The laboratory animals most susceptible to the pneumococcus are 

 the rabbit and the mouse. Fresh cultures in bouillon containing 10 

 per cent, of ox serum kill these animals on subcutaneous or intraperi- 

 toneal inoculation in doses as small as 0.0000001 c.c. However, animals 

 thus treated do not develop pneumonia, but die of general septicemia. 

 It has been found by examination of the sputum and by lung puncture 

 that the virulence of the coccus abates day by day as the disease 



