IMMUNIZATION 141 



may be introduced into the body in different ways, 

 by direct injection into the veins, or under the skin, 

 so-called subcutaneous injection, or in the muscles, 

 intramuscular injection. From the point of injection 

 the antitoxin more or less rapidly finds its way into the 

 blood it is therefore said to be haemotropic. After 

 intravenous injection the blood contains the antibody 

 from the time of injection onwards. MADSEN and 

 JORGENSEN have made a great number of measure- 

 ments regarding the blood's content of agglutinin im- 

 mediately after its injection into the veins of goats, 

 cats, or rabbits. They found that the agglutinin was 

 rapidly spread in the blood so that the content was 

 just as great as if the agglutinin had been evenly 

 distributed in the animal's blood-mass. Only rabbits 

 made an exception. They behaved as if 23 per cent 

 of the agglutinin had been lost immediately. As 

 we will see later on, the antibodies rapidly vanish 

 from the blood in the time just after the injection, 

 but such an immediate decrease as in this special 

 case with rabbits has only been observed with these 

 animals. 



The change of the concentration of diphtheria 

 antitoxin in a goat's blood after intramuscular or 

 subcutaneous injection is shown by the diagram (Fig. 

 33) given by LEVIN. It indicates that the blood's 

 content of antitoxin after ten hours is about 25 times 

 greater when the injection has been intramuscular 

 than if it has been subcutaneous. After twenty 

 hours the intramuscular injection still has the four- 

 fold effect of the subcutaneous one. Only after 60 



