220 Professor Svante Arrhenius [June 0, 



B, the ol)served quantity, are extremely yreat (in the proportion of 

 1 to 5000 in the one case and 1 to 800 in the other), and the errors 

 of observation are relatively important. Under such circumstances it 

 may be regarded as proved that the equation given above represents 

 the phenomenon with a high degree of accuracy. 



VII. — Influence of Foreign Substances. SENsiBiEisATOiis. 



In many cases it has been found that the presence of certain 

 salts is necessary, or in some cases favourable, for the reactions 

 under consideration. Tiie necessity of certain salts (especially salts 

 of Ca, Ba or Sr) for the precipitation of casein from milk by means 

 of rennet has already been alluded to. In this case probably a chemi- 

 cal reaction takes place. The coagulation of blood-plasma behaves in 

 the same manner, salts of calcium and analogous metals playing the 

 same role as in the precipitation of casein from milk. 



In other cases, as in the agglutination of bacilli, the salts seem to 

 exert a similar influence as in the sedimentation of particles suspended 

 in a fluid. The trivalent positive ions, such as Al, act more power- 

 fully than divalent ions, such as Zn, Mg, Cd, and these latter greatly 

 exceed the monovalent ions, such as K or Xa. The H-ion has a very 

 strong action. The bases seem to hold back the agglutination just 

 as in the sedimentation of suspensions. These regularities are not 

 very well marked in all cases. 



Other substances, especially albuminoids, such as serum from 

 blood or gelatin, diminish the agglutination. The agglutinating 

 cells are probably coated with a thin skin of these albuminoids, 

 wherel^y their properties become changed. 



In hemolysis by means of different bases, such as KOH, 

 NaOH, or LiOH, the presence of their neutral salts has a diminish- 

 ing action. Equivalent quantities seem to exert the same influence. 

 Madsen and Walbum found that about double the quantity of acid 

 or of base is necessary for complete hemolysis if the red blood- 

 corpuscles are suspended in a salt solution, as when they are sus- 

 pended in an isotonic solution of cane-sugar. Ammonium-salts have 

 a very strong retarding effect on hemolysis by means of ammonia, 

 acetates on the hemolytic action of acetic acid. Probably the velocity 

 of reaction here plays a role — under such circumstances this action 

 is easily explained. 



Imnu;ne l)odies, alexins and agglutinins are, according to experi- 

 ments of Bordet and Gay, absorbed in a higher degree in red blood- 

 corpuscles if these are suspended in a salt-solution than if they are 

 suspended in blood-serum. The anti-poisonous action of different 

 natural sera may probably be ascribed to this peculiarity. Here 

 evidently a chemical union of the albuminous substances in the 

 serum plays the chief role. 



