1911] on Physical C/tpmisfri/ (iiid the Dortrine of Immunity. 211 



hemoglobin, to the surrounding; fluid, whicli is tliereby coloured red- 

 This is easily observed if the l)lood-ct)rpuscles are allowed to subside 

 for a certain time, generally 12 to 24 hours, in an ice-safe. The 

 strength of the colour may be measured colorimetrically, so that 

 quantitative results are easily obtained. Such antibodies are called 

 hemolysins, and play an important role. 



Other antibodies obtained in this manner are called agglutinins, 

 because they agglutinate the red blood-corpuscles to aggregates which 

 subside or stick to the walls of the vessel containing the emulsion of 

 blood-corpuscles from animals of the same species as the injected 

 corpuscles. In tliis case, as in experiments on hemolysis, the blood- 

 corpuscles are separated through centrifugation from the blood- 

 serum, and then suspended in a solution having their own osmotic 

 pressure, in general 0'9 per cent, solution of sodium chloride ; other- 

 wise the blood-corpuscles may be attacked by the surrounding fluid 

 itself. For instance, pure water hemolyses red blood-corpuscles very 

 rapidly. 



If bacteria are injected, the blood-serum contains substances 

 which may attack the bacteria, so that they slowly disappear — those 

 antibodies are called bacteriolysins — or the antibodies may agglu- 

 tinate the bacteria, then they are called bacterio-agglutinins. These 

 antibodies, just as the hemolysins, are very specific, so that they do 

 not react with other bacteria except those which were injected. They 

 are therefore used to discriminate bacteria from each other, which is 

 of great use in determining the cause of illnesses. The high degree 

 of specificity indicates a chemical action. 



If a fluid antigen, as common egg-white or blood-serum, is 

 injected, the serum of the injected animal contains an antibody called 

 precipitine, because on mixing with egg-white or a serum of the 

 same kind (i.e. taken from an animal of the same kind) as that 

 injected a precipitate is formed. Even this reaction is in a high 

 degree specific. 



II. — Spontaneous or Catalytic Destruction of AntiCtEnes 

 OR Antibodies. 



A great number of these substances are rapidly destroyed at high 

 temperatures (over 50° C). In order to find the rate of destruction, 

 one determines the relative quantities which are necessary to add to 

 the reacting substance, e.g. a given quantity of a standard emulsion 

 of red blood-corpuscles or bacteria, or a given quantity of an 

 albuminous substance, in order t:hat the reaction — hemolysis, agglu- 

 tination, precipitation — shall be of the same order of magnitude. 

 Madsen and his pupils have performed a great number of such 

 experiments. It was found in all cases that the laws of physical 

 chemistry govern this phenomenon. As an instance, I give the 

 figures for the 



P 2 



