1906.] On Opsonins in Relation to Red Blood-cells. 3 



by hand or in a motor-driven shaker. The mixture was then centrifugalised 

 and the supernatant liquid pipetted off (great care being taken to ensure the 

 complete removal of the red blood-cells). 



The washed red blood-cells of 0*005 c.c. of guinea-pig's blood were next 

 added to 1 c.c. of the deopsinated serum, and the whole agitated for two hours 

 at 37° C. The sensibilised red cells, after being washed in 0*85 per cent, 

 sodium chloride solution, were added in excess to the leucocytes of the 

 guinea-pig in inactivated guinea-pig serum and kept on a warm stage (37° C.) 

 for two hours. The leucocytes were then examined under the microscope 

 and the percentage containing red blood-cells noted, 2000 to 4000 leucocytes 

 being enumerated. The percentages thus obtained are only approximately 

 correct,* as will be readily understood by reference to Table III, but 

 by making a number of tests under conditions as nearly as possible identical 

 in respect of every detail, fairly concordant results are obtained. 



The results, given in Table I, showed that it was possible to remove 

 opsonin from the serum employed, provided that a sufficient number of red 

 cells were used. After the red blood-cells of one or more parts of guinea- 

 pig's blood had acted upon two parts of the serum of Eabbit A, the serum 

 had completely lost its power of sensibilising red cells ; in other words, it no 

 longer contained opsonin in recognisable amount. If the red blood-cells of 

 one part of guinea-pig's blood were shaken with four parts of serum, sufficient 

 opsonin was usually left in the serum to sensibilise red cells; this was 

 especially the case when the period for deopsination was short. In 

 Table I no indication of the degree to which opsonin is removed is afforded 

 beyond the fact that a period of five minutes is too short to effect complete 

 removal at 37° C. 



The enquiry now presents itself, how much serum is required to sensibilise 



the red blood-cells of a given volume of guinea-pig's blood ? To investigate 



this point the series of observations recorded in Table II was undertaken. 



* The degree of phagocytosis obtained, apart from the degree to which sensibilisation 

 of the red cells has been carried, depends chiefly upon the uniformity and the closeness 

 of distribution of leucocytes and red cells. To secure the maximum degree of 

 phagocytosis the cells must be evenly distributed and the leucocytes must not be 

 separated by more than a few cell breadths from the erythrocytes, for leucocytes do not 

 appear to recognise the presence of the latter until their processes come in contact with 

 them. Difficulty was occasionally experienced owing to the occurrence of some degree of 

 agglutination of the red cells after treatment with the rabbit's serum ; separation could 

 usually be effected by shaking, provided the proportion of serum employed was not too 



great (i.e., ~- not above -£$, compare Table III). The condition of the leucocytes also 



affects the degree to which the red cells are taken up. If a sufficiently extended series 

 of tests are made the condition of the leucocytes tends to become the same in each 

 experiment. 



B 2 



