AGGLUTINATION AND DISSOLUTION. 177 



is no longer detectable. So, for example, in a mixture of one 

 part of rabbit blood, three parts of active serum and six parts of 

 hen serum the corpuscles are dissolved without any appreciable 

 delay. 



In order to determine more clearly the effect of the "anti-agglu- 

 tinin" in the serum, hen serum heated to 55 degrees and therefore 

 without dissolving property may be used; such a serum still agglu- 

 tinates very energetically an equal volume of rabbit blood. For 

 example, the following mixtures are prepared : 



Tube A, defibrinated blood, one part; active serum, ten parts; 

 hen serum, 55 degrees, one part. 



Tube B, defibrinated blood, one part; normal rabbit serum, ten 

 parts; hen serum, 55 degrees, one part. 



Agglutination is rapid and very strong in mixture "B" and is 

 negative or extremely feeble in mixture "A." 



When the active serum is mixed with hen serum a precipitate 

 is formed. We might imagine that the active serum does not con- 

 tain, strictly speaking, an antitoxic substance, but that the precip- 

 itate in its formation removes the harmful substances of the hen 

 serum and so renders it inactive. This objection, however, is not 

 well founded, as is shown by the fact that active rabbit serum 

 heated to 70 degrees loses the property of producing a precipitate 

 with serum, but still manifests its anti-agglutinating properties. 

 It retains, moreover, the property of preventing the dissolution 

 of corpuscles by hen alexin. 



This shows that the substance that opposes destruction by alexin 

 is quite different from alexins themselves. 



The serum of a guinea-pig vaccinated against rabbit blood also 

 shows antitoxic properties, but only to a slight extent. 



II. ANALOGIES BETWEEN SPECIFIC AND NORMAL SERA. ANAL- 

 OGIES BETWEEN SUBSTANCES ACTIVE AGAINST BACTERIA 

 AND THOSE AFFECTING BLOOD CORPUSCLES. 



It is well known that the various properties in specfic sera are 

 also present to a slight degree in normal sera. They are manifest 

 by an agglutinating action or dissolving action either on bacteria 

 or on corpuscles. It is quite natural to believe that the properties 

 acquired by the animal body as a result of immunization are only 



