BLOOD RELATIONSHIP 325 



But, practically, the matter is simplified by the fact 

 that little if any attention need be paid to the effect of 

 the donor's serum upon the recipient's .corpuscles. It is 

 of the utmost importance to know that the recipient's 

 serum will neither agglutinate nor dissolve the donated 

 corpuscles, for only under these circumstances should the 

 transfusion be effected. It is of far less importance to 

 know that the donor's serum will agglutinate or dissolve 

 the recipient's corpuscles, for should that be the case, the 

 transfusion may be practised, seeing that the quantity of 

 donated blood, not being more than one-tenth or one- 

 fifth of the total blood bulk, meets with a dilution that 

 usually makes the offensive action of the serum upon the 

 corpuscles impossible. 



In practice it is not necessary to know to which of the 

 various groups the recipient and donor belong; all that is 

 necessary is to find out by experiment that when a drop 

 of blood drawn from the finger of the donor is mixed with 

 an equal volume of the serum of the recipient no aggluti- 

 nation or solution of the corpuscles takes place. 



When the subject of grafting is considered, it will be 

 found that the blood relationship of the scion and the stock 

 in both plants and animals probably has much to do 

 with determining the success or failure of the experiment. 

 Tissue taken from one animal and grafted upon another 

 survives or is destroyed in large measure according to 

 the blood relationship of the animals concerned. So 

 sensitive are the tissues in this particular that, among 

 animals successful grafting can rarely be performed 

 when specific differences obtain among them. 



It also appears as though this matter of blood relation- 

 ship with its affinities, indifferences, or repugnances 

 may explain the difficulties attending successful hybridi- 

 zation. The germinal cells of specifically different 

 organisms doubtless possess the same sensitivity to 

 heterologous cells that are manifested by the somatic 

 cells, so that, instead of fertilizing one another, they 

 remain indifferent to one another, repel one another, or 

 perhaps even destroy one another. 



