ABILITY OF BACTERIA TO PRODUCE DISEASE 101 



into the deeper tissues and through the lymphatics gain access to 

 the blood stream, thus giving rise to bacteremia or septicemia. 

 When organisms are present there in great numbers or are bunched 

 together or mixed with fibrin to cause thrombi and later emboli, 

 they may by thus blocking the circulation cause serious mechanical 

 injury. Emboli stationed in the capillaries of feebly resistant 

 tissues usually result in local lesions ; multiple abscesses may thus 

 be formed, producing the condition known as pyemia. It will 

 be noted that the term septicemia is applied to conditions in which 

 bacteria circulate and multiply within the blood, giving rise to 

 symptoms of general poisoning, without, however, the formation 

 of abscesses. In pyemia, on the other hand, abscesses are produced 

 in the internal organs and other parts of the body. 



The tissue changes produced by bacteria are either of a degen- 

 erative or a recreative nature. In the former resistance is lacking 

 and the tissue is finally disintegrated ; in the latter case there is 

 excessive activity on the part of the body cells, secretions are 

 increased, phagocytosis is marked, until finally the invaders are 

 either eliminated or gain the battle. 



A local inflammatory reaction presents different characters in 

 different conditions. It may be accompanied by an exudate serous, 

 fibrinous, or purulent in character ; it may be localized or show a 

 tendency to spread ; it may be followed by suppuration and lead 

 to necroses. In many diseases the reaction is somewhat protracted 

 and there is a tendency to the formation of new tissue. In leprosy, 

 tuberculosis, syphilis, etc., such formation frequently occurs in 

 separate foci so that nodules result. 



Changes unassociated with the presence of bacteria may occur 

 in certain organs, due to the action of bacterial poisons circulating 

 in the blood; secreting cells and the walls of blood vessels may 

 thus be permanently injured. Diphtheria poison produces marked 

 degenerative changes both in the spinal cord and in the peripheral 

 nerves. It is possible that some of the lesions of the nervous 

 system occurring in syphilis are due to toxin. 



Acute infections ordinarily pass through the following stages. 

 First occurs the period of incubation, which begins at the time of 



