BIOLOGY OF PNEUMOCOCCUS 55 



production of peroxide, it would now seem wise to conclude that 

 the self-dissolution of this organism is caused by the action of its 

 own intracellular ferments. 



Bile Solubility 



The biochemical reaction taking place in the autolysis of pneu- 

 mococci is also involved in the solvent action of bile on the pneumo- 

 coccal cell. It was Neufeld 972 who, in 1900, first discovered that 

 bile possessed this unusual property, a property which became of 

 great diagnostic value in differentiating Pneumococcus from 

 Streptococcus and other organisms, and which has since been 

 known as the "Neufeld phenomenon." He found that rabbit bile in 

 a ratio of 1 to 50, or often of 1 to 200 or 300, added to fresh 

 bouillon cultures of living pneumococci, within a fairly wide range 

 of temperature of the fluids, rendered them clear and transparent 

 in the space of a few minutes. The microscope failed to reveal any 

 formed elements, for there was rapid and complete dissolution of 

 the pneumococcal cells. The bile of other animal species and of 

 man, despite considerable variation in the content of bile-acid salts 

 and mucus, exhibited the same property. Bile from rabbits was the 

 most active, and clear, limpid bile was to be preferred to that 

 which was more viscous or cloudy. Its action was not altered by 

 previous heating, but no lysis took place if the cocci had first been 

 killed by heat. Neufeld thought this action was attributable to 

 cholic acid in combination with glycocol and taurin, since glycocol 

 and taurin alone are inactive. 



Nicolle and Adil-Bey (1907) 1007 preferred rabbit bile to that of 

 the ox because of its greater solvent action on pneumococci, but 

 better still were sodium cholate and sodium choleate. The authors 

 found that this property was shared, although to a somewhat less 

 degree, by quinolate, taurocholate, glycocholate, and least of all, 

 hypocholate. Bile-solubility was looked upon as a salient character 

 of Pneumococcus. 



The advantages of sodium taurocholate over whole bile, claimed 



