TKANSFUSIOST OF BLOOD 



827 



TABLE II 



*Time required for 1.5 c.c. of venous blood to clot in a test tube 8 mm. in diameter. 

 Upper limits of normal 15 min. 



occurs following transfusion. This may be due to a direct or indirect 

 effect of the transfused blood. Increased bone marrow activity may be 

 manifested not only by increases of young red cells but increases also of 

 platelets and marrow white cells above a level due to the transfused blood. 

 In other instances, when the regeneration is not so rapid, significant in- 

 creases of young red cells do not occur, but the platelets and marrow white 

 cells remain at a higher level than before transfusion. If a suitable for- 

 mation occurs the count of the red cells remains elevated and increases 

 while the transfused cells gradually cease to exist in the circulation. Such 

 a picture indicates that the bone marrow elements are being delivered into 

 the circulation at a desirable rate. 



Alteration in the white count following transfusion may be associated 

 with a mechanical redistribution of the blood in the same manner as the 

 red cells. Thus, elevation of the white count does not necessarily indi- 

 cate a general increase of bone marrow activity. A sharp leukocytosis 

 following transfusion may be only a further manifestation of a reaction 

 due to the foreign blood, as described on page S40, rather than a sign 

 of general marrow activity. Still the degree of leukocytosis indicates 

 roughly the ability of the marrow to produce blood even though the 

 transfusion may not be followed by an increase of blood production. Al- 

 terations in the platelets may occur after transfusion in a similar manner. 



