102 BACTERIOLOGY FOR NURSES 



infection and continues until the first symptoms appear; the 

 period is more or less constant for each species of microorganism. 

 According to the theory of Vaughan the bacteria are at this time 

 multiplying enormously and for their food are using the proteins 

 of the body. Thus the soluble proteins of the blood and lymph are 

 being converted into bacterial cells. The process is entirely one 

 of construction ; no bacterial poisons are being eliminated to dis- 

 turb the body and consequently no symptoms appear. The 

 period of incubation is nevertheless critical since a strongly virulent 

 organism will develop with great rapidity and consequently con- 

 sume a large amount of protein. 



The second state is marked by the appearance of symptoms. 

 The body cells have become aware of the presence of the invaders 

 and are now pouring out ferments they have generated, which kill 

 many of the bacteria and decompose their protoplasm into simpler 

 substances, some of which are poisonous and produce the general 

 symptoms of intoxication. 



Then follows a period of high fever and the disease is at its height. 

 Special symptoms appear according to the organs involved. The 

 struggle between the invasive forces of the parasite and the defen- 

 sive forces of the body nears a climax ; supremacy seems to be first 

 with one side, then with the other. Finally the battle ends, and 

 if the body cells have proved victorious the symptoms begin to 

 disappear and a period of convalescence commences, during which 

 the body gradually overcomes the effects of the bacterial invasion 

 and returns to a state of health. The latter period is decidedly 

 critical ; undue exertion or errors in diet may further weaken the 

 already exhausted tissues, thus lowering their resistance and lead- 

 ing to a relapse. 



Degrees of Infection. When an infection occurs with a partic- 

 ularly virulent microorganism there may be so much poison liber- 

 ated that the cells of the body are paralyzed and completely over- 

 come. In such a case instead of a high fever being produced the 

 temperature drops to subnormal, and rapid prostration and death 

 of the patient quickly ensue. Such an infection is termed a malig- 

 nant infection. 



