SERUM ENZYMES 537 



separate preparations showing, one a very transparent, the other a 

 very turbid, condition. 



The Bordet-Danysz phenomenon has already been discussed, but 

 is another case in point. It consists of the fact that if to a definite 

 amount of antitoxin a definite quantity of toxin is added, the re- 

 sult is one of greater toxicity in the mixture if the poison is added 

 to the antitoxin fractionally than when the entire amount is added 

 at once. An interesting difficulty of this phenomenon is the fact that 

 such a reaction seems to force upon us the assumption that the toxin- 

 antitoxin union is not reversible, whereas later work on immuniza- 

 tion with neutralized mixtures of these substances seems to necessi- 

 tate the assumption that within the body they are reversible. 



It is a consideration of these and many other apparently physi- 

 cal factors of immune reactions which has led experimenters to seek 

 to utilize physical changes for practical serological purposes. One 

 of the reactions resulting from such studies is that known as Weich- 

 hardt's Epiphanin reaction. Weichhardt noticed that when two solu- 

 tions of toxin and antitoxin are brought in contact with each other on 

 exactly horizontal glass plates, diffusion takes place between them 

 much more rapidly than in controls in which one or the other, antigen 

 or antibody, was lacking. He tested this at first on the horizontal 

 glass plates by adding coloring matter to the two solutions and ob- 

 serving its diffusion currents. Later he developed a method in which 

 he tried to determine such increased diffusion by means of a delicate 

 chemical balance. His method, briefly described in his own words, 

 was as follows : a To the two arms of scales, to the right and left, a 

 little bell-shaped jar is attached into which dilutions of serum are 

 placed, on the one side specific immune serum, on the other normal 

 serum. These little bell-jars are closed at the bottom with 

 'Schleicher-SchiilP filter paper and are immersed into solutions con- 

 taining antigen in salt solution. Through the filter-paper mem- 

 brane diffusion takes place, and in observations carried on for from 

 several hours to several days it can be determined that the scales 

 sink on that side in which specific immune serum had been placed 

 into the little bell- jar. In other words, the antigen solution which 

 is contained in the salt solution diffuses more rapidly on the side on 

 which the specific immune serum was present. In consequence, the 

 weight of the little bell increases and a definite reading can be made." 

 Similar observations have been made by other observers, Kraus and 

 Amiradzibi doing the experiment as follows : they employed a U-tube 

 in the connecting horizontal part of which there was a glass stop- 

 cock. Into one side they put diphtheria toxin with a little aqueous 

 methylene blue, and into the other side antitoxin. For each experi- 

 ment two controls were set up, one with salt solution and the other 

 with normal horse serum, and they noticed that after a definite period 

 of time after the stopcock connecting the two had been opened, 



