102 



INFECTION 



to turn a revolving wheel until exhausted before they were inoculated; 

 similarly of four guinea-pigs who were placed in a cage so constructed 

 that they were forced to keep moving for one or two days three died in 

 from two to nine days after the experiment. Smears and cultures made 

 from the livers, spleens, and blood gave positive results. 



(6) Previous infection with the same or another infectious disease 

 may predispose the individual to renewed infection. Thus some in- 

 fections, such as erysipelas, furunculosis, acute rheumatism, pneumonia, 

 and influenza, not only fail to leave the body-cells immune, but actually 

 predispose to second attacks. Whether the microorganisms of these 

 diseases are not all destroyed, but are retained in the system and become 

 active when the general vitality is lowered, or whether a new infection 

 occurs, is not definitely known, and probably either may occur. 



One attack of an infectious disease may weaken the tissues and 

 render them susceptible to an infection of a different nature. Thus 

 the acute exanthemata may follow one another, and tuberculosis may 

 supervene upon any of them. 



(c) Malnutrition exerts some effect on the resistance to infection. 

 Thus the terrible epidemics of plague, cholera, typhus fever, and typhoid 

 fever which have followed in the wake of famines in Europe and Asia 

 during the past centuries are examples of the influence of malnutrition 

 as a factor in predisposing to disease. The tendency of marasrriatic 

 infants to develop enterocolitis, thrush, bronchopneumonia, and other 

 infections, and of scorbutics to local infections of the mouth, illustrates 

 the influence of insufficient food in decreasing the resistance to disease. 

 Here may also be included local malnutrition, such as loss of nerve or 

 blood supply, predisposing to local infection, especially with pyogenic 

 microorganisms. 



(d) Diet produces some variation in the resisting powers to infection. 

 For example, the ordinary wild rat is not susceptible to anthrax unless 

 it is fed for a week or more on coarse dry food, when it become sus- 

 ceptible. Here, of course, malnutrition may come in intimate relation- 

 ship with diet, as an inefficient diet may greatly lower the general 

 resistance. The influence of diet is particularly noticeable from the 

 fact that the diseases of carnivorous animals are not the same as those 

 that affect herbivorous animals, and that each class is frequently im- 

 mune to some of the diseases that attack the other. 



(e) Intoxications of various kinds predispose to infections. Thus it 

 is a common clinical observation that excessive indulgence in alcoholic 

 beverages predisposes to infections, notably pneumonia. Abbott 1 has 



. Exper. Med., 1896, 1, No. 3. 



