54 



Prof. A. E. Wright. On the Measurement of [Aug. 5, 



lies below 0° ; in the case of the alkalies our own experiments have 

 shown that the curves, which have usually been represented as 

 straight lines or flat parabolas, all exhibit inflexions, in the case of the 

 alkalies, LiOH, NaOH and KOH at about 40°, and in the case of the 

 alkaline earths, Ca(OH)2, Sr(OH) 2 and Ba(OH)2, at about 25° ; in the 

 case of the less highly ionised salts, such as magnesium sulphate, the 

 inflexion also lies below 100°, but in the case of salts such as potassium 

 chloride, which have a high coefficient of ionisation in solution and are 

 also electrolytes per se in the fused state, the inflexion lies above the 

 boiling-point of the solution.] 



" On the Measurement of the Bactericidal Power of Small Samples 

 of Blood under Aerobic and Anaerobic Conditions, and on the 

 Comparative Bactericidal Effect of Human Blood drawn off 

 and tested under these Contrasted Conditions." By A. E. 

 Weight, M.D., Professor of Pathology, Army Medical School, 

 Netley. Communicated by Professor J. R. Bradford, F.R.S. 

 Eeceivecl April 7, 1902. Received in revised form August 5, 

 1902. 



Section I. — Method of Measuring the Bactericidal Power of the Blood 

 under Ordinary (Aerobic) Conditions. 



As a preliminary to placing on record certain observations made in 

 connection with the bactericidal power of human blood, I propose to 

 describe in detail the technique which has been elaborated by me with 

 a view to carrying out these and similar investigations. 



A measurement of the bactericidal power of the blood involves in 

 the first place a standardisation of bacterial culture employed. 



I. Standardisation of the Bacterial Culture employed. 



A standardisation which would seem to satisfy all practical require- 

 ments can be achieved (a) by employing in the course of a series of 

 experiments one and the same stock of bacteria ; (b) by employing in 

 each experiment a young (e.g., a 24 hour old) culture ; (c) by determin- 

 ing in each case the number of living bacteria contained in a measured 

 volume of that culture. 



The determination last mentioned* involves — -first, the making of a 



* (Added 3.8.02.) Where, in lieu of the number of living bacteria, the total 

 number of bacteria in a culture is to be determined, this can be directly deter- 

 mined under the microscope by the method I have described in the ' Lancet ' of 

 July 5, 1902. 



