30 Mr Ponder, On the examination of 



On the examination of living leucocytes in vitro. By Constant 

 Ponder, M.A., Emmanuel College. [Communicated by 

 Mr W. E. Dixon.] 



[Bead 23 November 1908.] 



The satisfactory examination of living leucocytes has presented 

 many technical difficulties. Methods have been mainly employed 

 whereby the movements, and escape of the leucocytes from blood 

 vessels, have been observed in the tissues of a living animal, or 

 the leucocytes have been obtained, in the fluid from serous 

 cavities, abscesses, or blisters, and studied in suspension, in a 

 " hanging drop." It is possible to obtain a fairly clean pre- 

 paration by centrifugalizing citrated blood, as in Wright's opsonic 

 method, and by the usual laboratory process, in which a thin film 

 of blood, prevented from drying, is examined on a warm stage ; 

 a few white cells can be found, but their appearance is much 

 masked by the presence of the red cells. 



The method which I am going to describe gives a perfectly 

 clean preparation of a great quantity of leucocytes obtained direct 

 from any blood ; the leucocytes can be kept alive for some time, in 

 order that their movements and other physical properties can be 

 studied, while the manipulations are so simple that they may be 

 carried out by a class of students. I believe, moreover, that the 

 method may be useful in research work on these most important 

 cells, for it is also possible in this process to allow leucocytes free 

 movement for some hours, in relation to extraneous substances 

 introduced in their midst, in other words to study their chemiotaxis 

 " in vitro," or again, one can actually watch their behaviour, when 

 moving amongst a suspension of bacteria. One can also suggest 

 the interest of observing the behaviour of pathological cells, such 

 as those obtained from the blood of a patient suffering from one 

 of the severe anaemias. 



The method. The necessary apparatus is to be found in all 

 pathological and physiological laboratories, the only unusual 

 material needed is modelling clay or " Plasticine," which can be 

 obtained anywhere. 



The essential point is the preparation of a blood-chamber, 

 whereby the white cells are allowed to escape from the clot and 

 adhere to the surface of a slide, or coverslip, the clot being 

 afterwards removed. 



To make this chamber a morsel of plasticine, half the size of 

 a pea, is rolled out until it is as thin as the lead of a pencil and 

 about an inch and a half long ; this is then taken and gently 



