ON THE NATURE OF TOXINS 51 



At the same time, it is quite certain that these substances play 

 some part in the production of the symptoms of various diseases. 

 The anaemia which develops so rapidly in acute sepsis is well 

 known, and is one of the most constant symptoms of that affec- 

 tion ; it is to be ascribed, in part at least, to the destruction of 

 the red corpuscles by the haemolysins elaborated by the strepto- 

 cocci, staphylococci, or colon bacillus, if these happen to be the 

 infective organisms. The blood of an animal which has been 

 injected with virulent streptococci is found to contain haemolysin, 

 and that this is actually the haemolysin produced by the strepto- 

 coccus is shown by the fact that the action of this serum is 

 restrained by the addition of serum from an animal treated by 

 injections of streptococcic haemolysins. Thus it is proved that this 

 organism elaborates its haemolysin in vivo as well as in vitro ; and 

 several observers have found that it is those species of strepto- 

 coccus which are specially virulent to animals and man that 

 form haemolysins, the harmless ones doing so to a small extent, 

 if at all. The same is true for staphylolysins. Further, when 

 a culture of streptococci which is but slightly virulent and forms 

 but little haemolysin is rendered more virulent by " passage " 

 through rabbits, its power of forming streptocolysin is increased. 



These facts render it certain that some at least of the bac- 

 terial haemolysins act, to some extent, as exotoxins, though the 

 organisms producing them certainly form other and more im- 

 portant specific poisons. We may consider them as accessory 

 toxins of comparatively little pathological importance. 



The similarity in nature of the bacterial haemolysins and the 

 specific exotoxins is shown by the fact that (in the case of strep- 

 tocolysin, and probably in others) they can become converted into 

 htzmolysoids, analogous to toxoids. This is shown as follows : 

 Streptocolysin becomes inert in a week. If a small quantity of 

 blood-corpuscles be added to an excess of this inert solution, and 

 then thoroughly washed and added to a fresh and active solution 

 of streptocolysins, they will not be dissolved ; the corpuscles had 

 evidently become saturated with inert haemolysoid, and are now 

 unable to take up any haemolysin, their combining powers being 

 satisfied (see Fig. 6). 



The chief bacterial haemolysins are those formed by the tetanus 

 bacillus, the staphylococcus, the Streptococcus pyogenes, the B. pyo- 

 cyaneus, B. coli, and the typhoid bacillus. Their more important 

 features will be recapitulated briefly. 



42 



