228 THE INCOME OF ENERGY 



The corpuscles are agglutinated and their hae- 

 moglobin is set free. The mixture becomes red, 

 clear and limpid in two or three minutes. With 

 the microscope nothing can be found but the 

 stroma of the corpuscles, more or less deformed, 

 very transparent and scarcely visible. 



Tho continued presence of blood corpuscles 

 of the rabbit in the blood of the guinea-pig has 

 developed in the latter the power to agglutinate 

 the corpuscles and to set free their haemoglobin. 

 It is thus that the guinea-pig protects itself ; it 

 acquires immunity. 



3. Heat 1 c.c. of serum t) 55 C. for half an 

 hour. Add 0.5 c.c. of this to 1.5 c.c. defibrinated 

 rabbit blood as in Experiment 2 B. 



The serum which was heated to 55 C. no 

 longer destroys the corpuscles, but still strongly 

 agglutinates them. 1 



Evidently the agglutination of the corpuscles 

 and tho setting free of the haemoglobin (termed 

 "laking") are effected by different substances. 

 The agglutinating body resists a temperature that 

 destroys the blood-laking body. 



4. To the mixture used in the preceding experi- 

 ment, add 2 c.c. of fresh serum from a normal 



1 A very slow destruction of the red corpuscles may be ob- 

 served. This, however, is due to the fresh serum in the 1.5 c.c. 

 defibrinated rabbit blood, as will be evident from Experiment 4. 



