AGGLUTINATION AND DISSOLUTION. 169 



with accuracy as to dosage. For example, in such an experiment 

 the following mixtures would be made: 



Mixture (a) : one part of defibrinated hen blood; four parts of serum A (heated 

 for one-half hour to 55 degrees) ; three parts of unheated serum A. This is the 

 control. 



Mixture (6): one part of defibrinated hen blood; four parts of serum B (55 

 degrees) ; three parts of unheated serum A. 



A drop from each mixture is suspended on a hollow ground slide. In mixture 

 (a) the corpuscles remain intact. On the following day a few free nuclei are found, 

 but the destroyed corpuscles are in the great minority. As we already know, 

 normal rabbit serum has a slight hemolytic activity. In mixture (6) the destruc- 

 tion of red blood cells occurs rapidly, so that at the end of an hour there are nothing 

 but free nuclei left. 



In comparing the dissolving activity of different fluids in such 

 an experiment, care must be taken to keep them at the same tem- 

 perature. The dissolution of red blood cells is very much accel- 

 erated by heat, as is the granular transformation of the cholera 

 vibrio. 



As this experiment clearly shows, there is no reason to suppose 

 that the injection of active serum into normal animals brings about 

 any secretion of a particular dissolving alexin which is not present 

 in normal serum. To all intents the substances injected have been 

 simply diluted in the body fluids of the recipient. Any experiments 

 that can be performed with active serum may also be done with the 

 serum of a passively immunized animal. 



Consequently, if we regard the proper substances of the active 

 serum as simply diluted in the body fluids without any further 

 change on injection into normal animals, we should also expect to 

 obtain a fluid which is exactly as active as serum B, by mixing serum 

 A with a certain amount of the active serum employed. Such a 

 mixture of active serum and serum A, should be made, to be sure, 

 in proportions that are comparable to the relation between the 

 amount of active serum injected and the amount of fluid in the 

 animal body. 



This is found to be true. In the preceding experiment serum 

 B (which was obtained from a rabbit that weighed about 2000 

 grams and had received 10 c.c. of active serum) shows activity 

 similar to that obtained by diluting 1 part of active serum with 

 20 parts of serum A. 



