218 GERMICIDAL SERA 



mal and immune sera consists of two parts, one of which is ther- 

 molabile and the other is thermostabile. This is probably true of most, 

 if not all, enzymes. The thermolabile part is now known as alexin 

 or complement; the thermostabile part is known as fixator, sensi- 

 tizer or amboceptor. The former is present in all sera and the 

 weight of evidence is that it is non-specific. The amboceptor is the 

 specific part. According to Ehrlich's theory the amboceptor, which 

 he has, at different times, designated as intermediary and immune body, 

 but which is now generally known as amboceptor, combines on the one 

 hand with the bacterial or other cell and on the other with the com- 

 plement. The union between the amboceptor and cell may take place 

 at low temperature (even at C, 32 F.), but the complement enters 

 into the reaction only at temperatures not far above or below that of 

 the animal body. The complement is destroyed by a temperature of 

 from 56 to 58 C., but the amboceptor is not injured at this temperature. 

 When a serum is heated to this temperature it is inactivated; its bac- 

 teriolytic or cytolytic action is interrupted because the complement is 

 destroyed, but the ambocepter is not impaired and the serum is reacti- 

 vated by the addition of fresh complement which exists in both normal 

 and immune, unheated serum. This applies to all cytolytic sera, 

 whether they manifest their activity on bacteria, red blood cells, sper- 

 matic cells or other kind of cell. According to Ehrlich's teachings the 

 union of amboceptor with cell on one hand and with the complement 

 by the other is chemical, while Bordet believes the amboceptor, which 

 he calls a sensitizer, acts as a mordant in coloring and the complement 

 may be regarded as a dye. In other words, Bordet's explanation 

 supposes the action of physical rather than chemical forces. 



To conclude this part of our subject, we may say that normal blood, 

 and the serum obtained from it, contains non-specific bactericidal fer- 

 ments or enzymes. These vary in amount, kind and efficiency in 

 different species. In a general way, the blood is a germicidal fluid and 

 it owes this function to the presence of proteolytic enzymes. In normal 

 blood these enzymes are not specific and they display marked, destruc- 

 tive action on certain bacteria, and are wholly without effect on 

 others. Living cholera cultures, in doses that might infect by way 

 of the intestines, can be injected into man subcutaneously or intra- 

 venously without ill effect. Cattle bear large injections of the organ- 



