TOXINS 27 



blood reaction and by refusing isolation. The toxins are not 

 essential to the life of pathogenic bacteria and some of the usually 

 virulent organisms may grow without toxin development. Toxin 

 productions may be lost and regained. The real object of the 

 toxins is not known, as it is not thought that bacteria gain any- 

 thing by producing disease. They are separate from the other 

 chemical bacterial products. Toxins may be divided into those 

 which are secreted through the bacterial cell wall and diffuse 

 through the median in which organisms are growing, the extra- 

 cellular or soluble toxins, and those which remain within the 

 bacterial cells and are only liberated upon their death and dis- 

 integration, the endotoxins. Closely related to the second class 

 are the so-called toxic bacterial proteins or plasmins. These do 

 not separate from the structures since bacteria which produce 

 them furnish a toxic mass if thoroughly washed, ground and 

 rewashed. 



Examples and Characters. Soluble or Extracellular Toxins. 



The best examples are those of the tetanus and diphtheria bacilli. 



In diseases caused by these germs, bacteria do not enter the body 



i fluids but the general manifestations are due to absorbed soluble 



I poisons. Such toxins are soluble in water; they are rendered inert 



i by heating, sunlight and some chemicals. They dialyze very 



i slowly and are not crystallizable. They may be precipitated with 



j the albumen fraction of the medium. They may be precipitated 



and dried, in which state they keep much longer than when in 



solution, and then are more resistant to heat. Curiously enough 



I the toxins may be destroyed by proteoly tic enzymes. Some toxins 



! are complex; the tetanus toxin for example, contains two elements, 



; one a dissolving power on red blood cells, the other a stimulator 



i of the motor system. They are specific for each organism. 



Endotoxins. These are exemplified by the poisons of the ty- 

 phoid and plague organisms. We know little of their chemistry 

 but we may assume that it is of protein material and similar to 

 that of the bacterial cell. These toxins are less rigidly specific 



