CYTOLYSINS 131 



vacuum, in vacuum after freezing, or on filter paper. In the hands of 

 certain workers various methods of this sort have proven more or 

 less successful but do not seem to be widely applicable. It is of im- 

 portance to keep in mind that under such conditions the desiccation 

 of serum does not remove the possibility of the destructive action of 

 light. Other methods of preservation include salting with sodium 

 chloride and also with sodium acetate. The former has been fairly 

 successful, but the latter has been completely abandoned. Another 

 method is salting and then freezing, but this has been found to be in 

 no way superior to freezing without salting. According to Bigger, 

 it is of extreme importance that the serum should be sterile to ensure 

 the success of any method of preservation. Browning and Mackie have 

 found that frozen serum kept at a temperature of -15 C. retains its 

 complementary power three months without appreciable loss. Noguchi 

 and Bronfenbrenner found that at 10 C. the serum loses one-half 

 its original strength at the end of twenty-four hours. If it is kept at 

 37 C. it loses two-fifths of its strength at the end of six hours; at 

 45 C. one-half hour exposure reduces it to one-third to one-half its 

 original strength ; at 50 C. 50 per cent, is lost in five minutes. They 

 have examined the rate of destruction at 55 and find that this goes 

 on quite irregularly and is not in proportion to the length of time. 

 The irregularity, however, presents a certain rhythm, i.e., a period of 

 greater destruction alternating with a period of less active destruction. 

 Reudiger has studied the preservation of frozen complement and finds 

 that at the expiration of one week whether the complement is made 

 up of serum of a single guinea-pig or the pooled serum of several 

 guinea-pigs the activity in the Wassermann is somewhat stronger than 

 with fresh serum. At the end of two weeks the frozen complement 

 gives results that are practically identical with the results obtained 

 with fresh complement, but after two weeks the frozen complement 

 gradually loses strength apparently more rapidly in mild weather than 

 in very cold weather. 



Variability of Complement. Complementary activity varies con- 

 siderably in different sera ; in the same serum it may operate differently 

 with amboceptors from several different species. The explanation of 

 this difference of activity has led to a difference of opinion as to the 

 exact nature of the complementary activity. Ehrlich and Morgenroth 

 and the German school take the position that a given serum contains a 

 considerable number of complements, whereas Bordet and his school 

 take the point of view that the complement in any given serum is a unit, 

 although they admit that complements in different sera may represent 

 a somewhat different constitution. 



Multiplicity of Complements. Ehrlich and Morgenroth were able 

 to show that the complementary activity of a serum could be divided 

 by means of filtration in the following respect. They showed that 

 complement for sensitized guinea-pig cells passes through the filter, 

 whereas complement for sensitized rabbit cells remains in the filter. 

 It has also been shown by thermal and chemical differentiation that 



