26 PRODUCTS OF BACTERIAL ENERGY 



sterile, but as a matter of fact, isolated pathogenic bacteria 

 such as colon and diphtheria bacilli, streptococci, and pneu- 

 mococci, have been found in the tissues and cavities of the body 

 in the absence of pathological evidence of their presence. 



Sixteen hours after death the blood and tissues teem with 

 bacteria that have wandered in from the intestines. It has been 

 shown that bacteria, even non-motile ones, can migrate through 

 the body during the agonal period. 



Bacteria may cause disease in the following ways : (a) mechan- 

 ically, a clump of bacteria may plug a capillary; (b) simply over- 

 whelm the tissues and absorb the oxygen (anthrax); (c) they may 

 cause new growths (tubercle) ; or false membranes to form in the 

 larynx causing suffocation (diphtheria); (d) ulceration of heart 

 valves causing cardiac insufficiency; (e) thrombosis in the veins 

 and arteries; (J) pus formation; (g) by generating toxins that 

 cause anaemias, or degeneration of important elements of the 

 nervous system, parenchymatous organs and the walls of the 

 blood-vessels. 



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 pathogenic for man, but not to swine. 



As emphasized 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, in causing a peculiar 



