176 A MANUAL OF BACTERIOLOGY 



the skin, but also of the mucous membranes, e.g. the 

 septic diseases, glanders, tetanus, etc. The extreme infec- 

 tivity of some diseases e.g. variola, scarlatina, influenza, 

 etc. may be due to the fact that infection takes place 

 by the respiratory tract. In certain instances the infec- 

 tion is conveyed in some special way, e.g. by mosquitoes 

 in malaria and in yellow fever. Nor is infection neces- 

 sarily confined to one mode of entrance ; in plague, for 

 example, infection by the skin is commonest in some 

 epidemics, but it is not infrequent by the respiratory, 

 and may occur by the digestive, tract. The infecting 

 agent may remain localised, giving rise to a local infection, 

 or it may be widespread through the body, a septicaemia, 1 

 bactericemia or general infection. The absorption of chemical 

 products from a local site of infection may produce general 

 symptoms ; this is intoxication, as occurs in cholera, in 

 which the microbe is present only in the bowel, in the 

 early stage oi diphtheria, in which the diphtheria bacillus 

 is limited to the membrane, and in a local abscess. 

 Fever is usually one of the results both of intoxication 

 and of general infection. 



The localisation of a particular infection may in some 

 instances be due to a selective affinity of the strain of the 

 organism for a particular tissue. Rosenow has given 

 evidence of this in the case of pathogenic streptococci. 

 He isolated streptococci from various lesions in man, 

 then injected the cultures intravenously into rabbits 

 and determined the site of the lesions in the inoculated 

 animals. Fourteen strains from appendicitis produced 

 lesions in the appendix in 68 per cent, of sixty -eight 

 rabbits injected, which is in marked contrast' to an 



1 " Septicaemia " and " a septicaemia " have different meanings. The 

 former is applied to a general infection with the so-called septic organisms, 

 the latter to a general infection with any organism. " Bacterisemia " is a 

 better term for the latter. 



