138 Mr. C. Russ. , An Improved [Feb. 21, 



slip transferred to a tube of litmus dextrose broth. Growth occurred within 

 24 hours. 



So far as the possibility of interplanetary bacterial life is concerned, then, 

 it is evident that bacteria in the fully dried state, if free in the interplanetary 

 vacuum, would be killed by the solar light and ultra-violet rays. 



And, as Sir James Dewar's experiments have demonstrated that the 

 ultra-violet rays will kill undried bacteria whilst in the frozen condition, at 

 the temperature of liquid air ( — 190° C), there is little to support the 

 hypothesis that the living protoplasm on the earth originally immigrated 

 from interplanetary space in a free or unincluded condition — that free, 

 particulate life has entered the earth's atmosphere as a result of light 

 propulsion, from extra-mundane space. 



An Improved Method for Opsonic Index Estimations, involving 

 the Separation of Red and White Human Blood Corpuscles. 

 By Charles Buss, M.B. Lond. 



(Communicated by Dr. A. D. Waller, F.B.S. Eeceived February 21, — Bead 

 March 14, 1912.) 



Opsonin is the name given by Sir A. E. "Wright to the substance in human 

 blood which mainly influences phagocytosis. In order to measure the 

 opsonin, equal volumes of normal serum, of a bacterial emulsion, and of 

 leucocytes are incubated to promote phagocytosis, and the number of bacteria 

 visible in a random sample are counted in a stained film preparation. By 

 repeating the experiment with a pathological serum, a ratio is obtained which 

 is known as the opsonic index. The method, however, has been found 

 inaccurate, and consequently fallen almost into disuse. Drs. Greenwood 

 and White pointed out the error of random sampling and, after elaborate 

 mathematical analysis, adjudged the "liability to error" on a single count to 

 occasionally exceed 20 per cent, from the mean or true figure. Clearly, 

 when the counts from two films are contrasted, the liability to error may 

 be doubled. 



This liability to error is due to the variation in content of different 

 leucocytes in the same film ranging from to 25 bacteria, and the resulting 

 total in 50 leucocytes will vary according to the field in which the operator 

 happens to make his count, i.e., one rich in high or low contents. 



