4 LECTURES ON IMMUNITY 



was at the commencement four arbitrary units. If we 

 inject a culture of the bacillus (e.g. Vibrio cholera*) into the 

 blood of a goat, it produces antibodies specific to just the 

 injected bacilli. Amongst these antibodies is one called 

 agglutinin, because it causes cholera bacilli to clump 

 together and sink to the bottom of the liquid in which 

 they are suspended. We may measure the concentration 

 of agglutinin in a liquid by a method to be described 

 below. 



The experiments, the results of which are given in the 

 curve, were carried out by Madsen and Jorgensen, 1 follow- 

 ing the subcutaneous injection of 40 c.c. of a culture of chol- 

 era bacilli into a goat. From the jugular vein of the goat 

 small amounts of blood were taken every day and exam- 

 ined as to their content of agglutinin. In the first two 

 days no increase in the quantity of agglutinin in the 

 blood serum was observed, but later on it rose rapidly 

 till it reached a maximum, " acme," on the eighth day, 

 after which it sank at first rapidly, then more slowly. 



The continuation of the curve illustrates an experiment 

 with the same goat, in which an injection of 5 c.c. of a 

 culture of cholera bacilli was made daily during the whole 

 period of research. Here the first period, in which no 

 agglutinin was produced, lasted four days, and the second 

 period, where the agglutinin increased, eleven days. 



Madsen has found that the decrease after the maximum 

 follows closely the equation for the velocity of a chemical 

 reaction : 



1 A. Jorgensen and Thorwald Madsen : "The Fate of Typhoid and Cholera 

 Agglutinins," Festskrift oed indviclscn af statens scrum-institut,'V\, 12, 1902, 

 Copenhagen. 



