24 PRODUCTS OF BACTERIAL ENERGY 



clump of bacteria may plug a capillary; or simply overwhelm the 

 tissues and absorb the oxygen (anthrax) ; they may cause new growths 

 (tubercle) ; or false membranes to form in the larynx causing suffo- 

 cation (diphtheria) ;^ulceration of heart valves causing cardiac 

 insufficiency; thrombosis in the veins and arteries; pus formation; or, 

 by generating toxins that cause anaemias, or degeneration of im- 

 portant elements of the nervous system, parenchymatous organs and 

 the walls of the blood vessels. 



w The tissues of certain animals are receptive for particular bacteria, 

 and the latter are therefore pathogenic to that animal. B. of swine 

 plague is pathogenic to swine, but not to man. B. typhosus is patho- 

 genic for man, but not to swine, y 



J As emphasizd above, the activities of bacteria are due to the 

 enzymes they produce. In the course of their life, bodies, called 

 toxins, are formed that have the power of producing illness in 

 higher plants and animals. These bodies are similar to the 

 enzymes. Both are produced in minute quantities. Their exact 

 chemistry is not known, and pure toxins, at least, have probably 

 never been isolated. We test for them by animal experiments 

 while the presence of enzymes may be observed upon artificial 

 culture media. Toxins of bacteria are not the only ones formed. 

 Castor bean produces a body classed among the toxins as does 

 the rattlesnake in its venom. These bodies differ from ptomaines, 

 also poisons, by being less resistant to heat, causing a peculiar 

 blood reaction and by refusing isolation both of which ptomaines 

 do not. 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 anything 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 medium in which organ- 

 isms are growing, the extracellular or soluble toxins, and those which 



