BLOOD TRANSFUSION 391 



already formed and at work. This is only one of a number of 

 tests that have been developed in recent years. Just as each 

 disease is caused by a specific kind of organism, producing a 

 specific kind of toxin or poison, so the blood forms specific anti- 

 bodies to fight each kind of organism or its toxins. 



Blood transfusion. It has been found that there are four types 

 of human blood. About 50 per cent of all people have one type. 

 After heavy losses of blood as in an accident or in an operation, 

 and in some illnesses, blood is sometimes injected into a vein of 

 the patient by transfusion from an artery of a donor. Before this 

 operation is performed, it is necessary to make a test to see if the 

 two persons have blood of the same type. This is done by means 

 of the agglutinin test. Red corpuscles of the person who is to 

 give the blood are added to the blood of the patient. If the red 

 corpuscles are agglutinated, then the bloods are of two different 

 types and transfusion cannot be made. Certain lysins called 

 haemolysins may also be present in blood that will dissolve foreign 

 red corpuscles of the volunteer in the blood of the patient. Tests 

 may be made for these haemolysins by adding washed red cor- 

 puscles of the volunteer's blood to the serum of the patient's blood. 

 If the corpuscles are dissolved, this blood cannot be used for trans- 

 fusion. 



Self-Testing Exercise 



Blood consists of a fluid part called (1) and three kinds of 



cells : (2) corpuscles, (3) corpuscles and (4) 



(5). Red corpuscles take up (6) by means of the 



(7) they contain. There are several kinds of (8) 



corpuscles, all of which are (9) in outline and have the 



power of (10). Those called (11) feed on bacteria 



in the blood. Blood clots because of the coagulation of the 



(12) it contains. This is brought about through the action of 



the substance (13). Plasma besides containing (14) 



contains antibodies. Among these are (15), (16), and 



(17). Lymph acts as a medium of exchange between the 



(18) and the (19) cells. Blood transfusions can be 



performed only if persons have blood of the same (20) . This 



can be found out by means of (21). 



