130 BIOLOGY OF PNEUMOCOCCUS 



beam of light at five-minute intervals. In some cases definite pre- 

 cipitation was noted in the homologous mixtures after five minutes' 

 incubation. To the remainder of the filtrate eight volumes of 95 

 per cent alcohol were then added, and, after mixing, the tubes were 

 set in the ice-box over night. The flocculent precipitate was col- 

 lected by centrifugation, the residue dried by heat under a stream 

 of air, and after salt solution was added, the solution was dis- 

 tributed into tubes for the addition of serum. The author tried still 

 another method for demonstrating the presence of precipitinogen 

 in patient's blood. To the serum collected as in the first procedure 

 distilled water and 0.2M sodium acetate-acetic acid buffer solution 

 with a pH of 4.6 was added. The mixture was then boiled until 

 coagulation was complete. The filtrate from the coagulum was 

 evaporated to dryness over a free flame, and heated carefully until 

 the odor of acetic acid was no longer present. The resulting dry 

 concentrate was extracted with sterile distilled water, the solution 

 cleared by centrifugation or by filtering through paper and the re- 

 sulting liquid used as a precipitating antigen against type serums 

 I, II, and III. The delicacy of this method was shown by the fact 

 that precipitinogen could be detected in the blood when blood cul- 

 ture remained negative. 



To repeat Amoss' conclusion: "The method requires less time 

 than the sputum culture or mouse method, but has no advantage 

 over the sputum extract method. It is useful for typing in cases in 

 which neither sputum nor urine can be obtained" ; to which might 

 be added, it furnishes to those who are not content with negative 

 or doubtful results one more aid in arriving at a type diagnosis. 

 Amoss also saw in this method, by detection of the soluble specific 

 substance in the blood, a means of judging the amount of serum 

 necessary and for following more closely the results of serum ther- 

 apy in lobar pneumonia. The intricacy of the procedure would bar 

 its use in the busy routine of the average hospital laboratory, but 

 it would be of service, where time and the facilities permitted, in 



