188 THE TOXINS PRODUCED BY BACTERIA 



only capable of producing toxins within the animal tissues, 

 and it has further been thought possible that bacteria, such as, 

 for example, the typhoid bacillus, which do distribute into 

 media intracellular toxins, might either produce these toxins 

 more readily in the tissues or might produce in addition other 

 toxins of a different nature. During recent years such toxins 

 have been much studied, and the name aggresdns has been 

 given to them. The evidence adduced for the existence of 

 these aggressins as a separate group of bacterial poisons is of 

 the following kind : An animal is killed by a dose of the 

 typhoid, dysentery, cholera, or tubercle bacillus, or by a staphy- 

 lococcus, the organism being introduced into one of the serous 

 cavities. After death the serous exudate, which in all these 

 cases is present, is taken, and centrifuged to remove the 

 bacteria so far as this can be done by such a procedure ; the 

 bacteria which are left are killed by shaking the fluid up with 

 toluol and leaving it to stand for some days. Such a fluid in 

 a dose which by itself has no pathogenic effect, has the property 

 of transforming a non-lethal dose of the bacterium used into one 

 having fatal effect. Further, the effects of the combined actions 

 of the bacteria and aggressins are often of a much more acute 

 character than can be obtained with toxic products developed in 

 vitro. The effects produced by aggressins are attributed to a 

 paralysing action on the phagocytic functions of the leucocytes. 

 The subject is full of difficulties, and in the case of certain of 

 the organisms employed results similar to those attributed to 

 aggressin action have been observed with the fluid obtained by 

 macerating living cultures, — the deduction being that in the 

 aggressins we are merely dealing with a particular type of 

 endotoxin. As evidence of the existence of a special group 

 of toxins, it has been stated that a special type of immunity 

 against the aggressins can be originated. Perhaps the most 

 important aspect of the controversy is the recognition of the 

 existence of toxins having an action on the leucocytes. A poison 

 causing death of these cells in connection with the pus-forming 

 action of the pyogenic cocci has been described under the name 

 of leucocidin, and Eisenberg records that in in vitro mixtures of 

 leucocytes and cultures of the bacillus of symptomatic anthrax 

 loss of motility and degeneration of the cells may be observed. 



The non-specific effects of toxins are responsible for the general 

 changes occurring in the greater number of the common bacterial 

 infections in man. 



Exotoxins. — In the cases of a few pathogenic bacteria the 

 media in which they are growing become extremely toxic. This 



