PHYSIOLOGICAL CHEMISTRY 465 



having destroyed something necessary for haemolysis. Is there any agglutination ? 

 Now add 1 c.c. rabbit's serum to some of the mixture of previously heated serum 

 and blood corpuscles ; haemolysis will occur. To another part add some serum 

 from an uninoculated (normal) dog. The same result will be obtained. 



The destruction of the complement by heating is called inactivation. That 

 inactivation destroys something which, though necessary for haemolysis, is yet a 

 normal constituent of serum, is shown in the above experiment by the fact that 

 reactivation of the haemolysin can be effected by addition of rabbit's serum ; i.e. 

 of the same serum that the erythrocytes are normally accustomed to. 



The complement, whatever its chemical nature may be, is a constant con- 

 stituent of serum, but under normal conditions it does not as a rule act on the 

 erythrocytes and cause haemolysis because of the absence of the immune body. 

 To produce the immune body, inoculation with foreign blood is usually necessary. 

 There are in general two views as to the mechanism by which these two con- 

 stituents of serum act in bringing about haemolysis. The French school believe 

 (with Bordet) that the immune body acts on the corpuscle as a mordant acts on 

 cotton in dyeing ; in other words, it sensitises the corpuscle towards the com- 

 plement (thus, the French call it the substance sensibilatrice). The German school 

 (headed by Ehrlich), on the other hand, believe that the immune body first of all 

 combines with the corpuscle, and that the complement then combines with the 

 attached immune body and acts through it on the corpuscle. 



It would be out of place here to give a detailed account of the experiments 

 that have been brought forward in support of these hypotheses, but one important 

 fact can be easily demonstrated, viz. that the immune body readily unites with 

 the corpuscle in the absence of the complement, and that the subsequent addition 

 of complement then causes haemolysis. 



EXPERIMENT VIII. Centrifugalise 5 c.c. of a suspension of washed rabbit's 

 erythrocytes, and then carefully remove as much of the supernatant fluid as 

 possible. This yields, as sediment, erythrocytes that are free of complement. 

 Now add to the erythrocytes 2 c.c. of inactivated serum from an immunised dog; 

 shake the tube to obtain complete mixing, and allow to stand for some minutes. 

 No laking occurs. Then fill up the tube with 0*9 per cent, sodium chloride and 

 centrifugalise. Pipette off the supernatant fluid and repeat the washing three 

 times, so as to remove all traces of the inactivated serum, which may be merely 

 adherent to but not combined with the corpuscles. Now add some normal serum 

 to the tube and warm to 38 C. : haemolysis occurs, the complement in the normal 

 serum having acted on the erythrocyte-immune body compound. 



The immune body acts, therefore, as a link uniting corpuscles with complement. 

 It may be considered to possess two combining groups, and is hence called an 

 amboceptor. One of these groups called the cytophilic group first of all 

 unites with a side chain of the erythrocyte, and then the other group called the 

 complementophilic unites with the complement, resulting in destruction of the 

 erythrocyte. That the reaction takes place in this order is demonstrated in 

 the following experiment : 



EXPERIMENT IX. Centrifugalise 5 c.c. of the above suspension of rabbits' 

 erythrocytes, and with a pipette remove as much of the supernatant fluid as 

 possible. Place the sediment in a test tube, and cool in crushed ice to zero. In 

 another test tube likewise cool 0'5 c.c. of immunised dog serum. Mix the cooled 

 corpuscles and serum, and keep them at for one hour, after which transfer the 

 mixture to a cooled centrifuge tube, and immediately centrifugalise. Then remove 



2G 



