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Scientific Proceedings (132) 



packed sedimented bacteria. Physiological salt solution (0.85 

 per cent.) was added to the sediment in the proportion of 150 to 

 200 volumes of salt solution to one volume of the packed or- 

 ganism. The organisms were thoroughly washed in this fluid, 

 and then re-centrifuged at a high speed for thirty minutes, until 

 the sediment failed to pack further. The supernatant salt solu- 

 tion was removed, and if necessary, the upper zone of the packed 

 bacterial column in the small calibrated portion of the vaccine 

 tube. Sufficient physiological salt solution was added to make a 

 1 per cent, suspension by volume. The suspension was subjected 

 to heat in the water bath for one hour at 60° C. to kill the or- 

 ganism. Tests were made for sterility. No preservative was 

 added. 



The nitrogen determination was made upon aliquot parts of 

 the killed bacterial suspension. 



The total nitrogen content of the bacteria was determined by 

 the micro-chemical method of Folin and Farmer. For this pur- 

 pose, 1 c.c. samples of the homogeneous suspension of the 

 organism were used for each estimation. The tests were made in 

 duplicate, and if the results did not closely agree in each in- 

 stance, the tests were repeated. It is noteworthy that the results 

 of such tests showed a close agreement. The total solids were 

 determined by placing 5 c.c. of the homogeneous suspension of 

 the organism in a small tared porcelain crucible, then removing 

 the water content in so far as possible in an electric oven kept at 

 a temperature of 65° to 70° C. Finally the crucibles were placed 

 in desiccator containing phosphorus pentoxide. A vacuum was 

 produced, then it was placed in the electric oven (65° to 70° C.) 

 until the crucible with its contents came to a constant weight. 

 From the total solid content of the dried solids of each speci- 

 men, the added sodium chloride (physiological salt solution used 

 in preparation) content was deducted, leaving the amount of 

 total bacterial solids. The percentage of bacterial nitrogen was 

 estimated upon this basis. 



In general, the nitrogen contents of the individual strains (ten) 

 in each of the four serological groups of pneumococcus were 

 approximately of the same amount, although an occasional ex- 

 ception was observed, either a slightly higher or a lower value 

 than the general mean, which did not alter the average to any 

 extent. This occurred in the Group I series of determinations 



