AGGLUTINATION AND DISSOLUTION. 137 



well as before, but does not destroy them, as is shown by the fact 

 that they retain their color and normal appearance. 



It is evident that there is a striking parallel between those changes 

 shown by vibrios subjected to cholera serum and those in red blood 

 cells affected by serum from an alien species. We have noted that 

 the clumping effect, which is more or less evident in both instances, 

 is due to substances which resist heating to 55 degrees or even 

 more; it has also been noted that the destructive properties neces- 

 sitate the presence of a more susceptible substance, which is de- 

 stroyed by heating to 55 degrees. In a general way certain analogies 

 are present in the sera of normal animals, as a weak clumping power 

 both for bacteria and red blood cells is frequently found in them; 

 normal sera, moreover, have usually some altering or destructive 

 effect both for alien red blood cells and susceptible micro-organ- 

 isms. As has already been noted, the cholera vibrio if attenuated 

 and only slightly resistant may show at least partial transformation 

 with a normal serum. 



If a normal animal is vaccinated with the cholera vibrio, the 

 original clumping and destructive properties of its serum are con- 

 siderably increased.* On account of the parallelism that we have 

 just indicated and on account of analogies in the action of sera on 

 cells and bacteria, a question immediately arises. Would it be 

 possible by injecting a normal animal with the defibrinated blood 

 of an animal of a different species to increase the clumping and de- 

 structive property of its serum for the corpuscles injected? Experi- 

 ment gives a positive answer to this question. Guinea-pigs were 

 injected intraperitoneally five or six times with 10 c.c. of defibri- 

 nated rabbit blood. f The animals stand this treatment very well. 

 After a time their blood is withdrawn and the serum is found to have 

 the following characteristics: 



First: When added to defibrinated rabbit blood it clumps the 

 red corpuscles energetically. For example, one part of serum will 



* We use the cholera vibrio as an example, although it is well known that 

 vaccination with other bacteria will also cause the appearance of agglutinating 

 power. The cholera vibrio, however, on account of its susceptibility is the best 

 organism to demonstrate the bactericidal substance. 



t These doses, first used by Dr. Bordet to produce a hemolytic serum, have since 

 been found in his hands, as well as those of other investigators, to be unnecessarily 

 large. Quite as good results can be obtained by injecting much smaller amounts, 

 for example, 1 c.c. (Ed.) 



