232 THE BLOOD 



the blood-vessels. In recent years a number of cannulas^ have been devised which 

 make a direct anastomosis possible and obviate the danger of clotting . The second 

 reason is intimately associated with the hemolytic property of the blood. As will 

 be shown later, the body fluids of different animals contain certain agents which 

 are prone to cause serious injury to the blood of the recipient. The constituents 

 primarily involved are the red cells which are destroyed in varying numbers until 

 a proper aeration of the tissues can no longer be effected. 



Clearly, therefore, the blood of the donor should first be tested as to its hemo- 

 lytic power before it can safely be introduced into the recipient. It may rightly be 

 assumed that the blood of a widely divergent species is not at all suitable for trans- 

 fusion, because its properties would most hkely be very unlike those of the blood 

 of the recipient. For similar reasons it may be concluded that the blood of an 

 animal that is closely related to the recipient, is least prone to incite hemolysis. 

 Thus, transfusions upon human beings will prove less dangerous and promise better 

 results if a near relative is selected as the donor. 



1 Carrel, Med. Record, Ixxxii, 1912, 1013. 



