128 



EXERCISE XXI 



Obs. 95. 

 Phagocytosis 

 and opsonic 

 power of 

 serum. 



yil. Draw up into the capillary part of the glass tube fitted with 

 the rubber teat a little of the layer of the washed leucocytes, the supernatant 

 fluid having been pipetted oif previously. The amount drawn up should 

 make a column about 15 mm. long in the capillary part of the tube. 

 Similarly draw up into the capillary a similar quantity of the bacteria emul- 

 sion, and then finally a similar quantity of the serum above the clotted blood. 

 Two air-bubbles will separate these successive three fluids with which the capil- 

 lary part of the tube is charged. Expel them upon a glass slide and mix them 

 thoroughly ; then draw the mixture into the capillary tube again, and place in 

 the incubator at 37° C. for 15'. 



VII.I. Similarly make a triple mixture of the washed leucocytes, the 

 bacterial emulsion, and of the serum from tube B, § VI (so-called ' patient's 

 serum'), whose opsonic index is to be ascertained, and place the mixture 

 in incubator for 15'. 



IX. After incubation the mixture is expelled on clean microscopic 

 slides and spread into films and dried. The dried films are then fixed 

 and stained with the Leishman stain. Examine with a one-twelfth oil- 

 immersion objective. The leucocytes are to be found along the edges of 

 the films. Each leucocyte may contain from 4 to 8 bacteria. Count the 

 total number of bacteria in 50 leucocytes. 



Having thus obtained a * count ' with the control serum mixture, 

 obtain in an exactly similar way a 'count' with the serum mixture for 

 which the * patient's serum ' was used. If 50 leucocytes contain 300 bacteria 

 after the control serum, and 50 leucocytes contain 90 after the 'patient's 

 serum ', the opsonic index of the latter is 



90 

 300' 



ANNOTATION 



Opsonic action was discovered by A. E. 

 Wright and S. E. Douglas, Proceed. Roy. Sac. 

 vol. Ixxii, p. 357 ; Sept. 1, 1903. ' The blood 

 fluids modify the bacteria in a manner which 

 renders them a ready prey to the phagocytes. 

 We may speak of this as an " opsonic ' effect 

 {opsono = I cater for ; I prepare victuals for), 

 and we may employ the term " opsonins " to 



designate the elements in the blood fluids 

 which produce this effect.' See Handh. of 

 Physiology, Halliburton, 14th ed., p. 476, 

 1919, and consult Ledingham, Jnl. of Hy- 

 giene, vol. xii, p. 320, 1917. For pathological 

 bearings of this exercise see Manual of Bac- 

 teriology, Muir and Kitchie, 6th ed., p. 122, 

 1913. 



