THE H.EMOLYTIC PROPERTIES OF ORGAN EXTRACTS. 275 



All these experiments show that the organ extracts will bear 

 heating to 62-68 C. for hours, and even 100 for several hours, with- 

 out suffering any change in their hcemolytic properties worth men- 

 tioning. In these experiments, in fact, we have been unable thus 

 far to find any limit for the thermostability of the organ extracts.. 

 We are therefore dealing with substances which withstand boiling 

 (coctostabile), and this fact in itself is sufficient to disprove the assump- 

 tion that they are "cytases." 



The next question, of course, is how such a fundamental divergence 

 between our results and those from Metchnikoff's highly esteemed 

 laboratory can be explained. We think we have discovered the cause 

 of this difference. It is as follows: 



In the above experiments it is of the greatest importance to shake 

 the fluid previous to testing its hsemolytic property; in that way the 

 more or less plentiful precipitate formed on heating is again uniformly 

 distributed throughout the fluid. Only the coagiihim produced by 

 heating possesses a hsemolytic action. According to our experience, 

 if a precipitate has been produced through heating, the dear -fluid 

 which is separated from this no longer possesses any hcemolysin what- 

 ever. If the precipitate is separated by centrifuge the clear fluid will. 

 be found inert; on suspending the sediment in the requisite quantity 

 of physiological salt solution a new emulsion is obtained which has 

 preserved the hcemolytic property. This is shown in the following 

 table. 1 



According to these experiments it would seem very probable that 

 the contradictory results obtained by us on the one hand and b}^ 

 Metchnikoff and Tarassevitsch on the other are due to insufficient 

 regard being paid by the latter to the precipitates formed in the 

 organ extracts on heating. 



If we assume that the hsemolytic, coctostable substance is present 



1 The coagula formed on heating may be so plentiful that they render an 

 exact observation of haemolysis exceedingly difficult. It is frequently seen that 

 haemolysis by means of heated organ extracts which are filled with coagula 

 proceeds very slowly; apparently the precipitates offer considerable resistance 

 to the escape of the hsemolytic substance. Naturally, this constitutes a source 

 of error, since with low temperature and too short a time for observation the 

 hsemolytic action is underrated. This may also explain the occasional weaken- 

 ing of heated organ extracts, to which we have already referred ; in that case 

 the weakening would not be due to a partial destruction of the hssmolytic 

 substance. 



