4 Introduction 



fibre of muscular tissue. In human trichinosis, however, the disease 

 picture is more complicated than in itch and leads us to assume that 

 there is some additional action of the excreta of the larvae in the 

 production both of the febrile state and of certain general phenomena. 

 In the nagana disease (transmitted by the Tsetse fly) there is equal 

 reason to admit the preponderating role of the ^mechanical action] of 

 tlie flagellated parasite (Trypanosoma) which obstructs the vessels 

 of the nervous centres. 



In the diseases which are set up by Fungi, such as ringworm and 

 aspergillosis, the purely mechanical element still appears to play the 

 more important part. Even certain of the bacterial infections mani- 

 fest this same character. Thus, there is no doubt that in chronic 

 tuberculosis in the guinea-pig, Koch's bacillus brings about a substi- 

 tution of tuberculous elements for the normal tissues, and this to 

 such a degree that, at the termination of the disease, there may 

 remain merely traces of the liver and of the lungs, and the animal 

 dies for want of these organs, whose normal action is no longer 

 possible. In the tuberculous guinea-pig the phenomenon of intoxica- 

 tion by the bacillary poisons plays but a secondary role; yet there 

 are examples of tuberculosis (as in acute miliary tuberculosis in man 

 or experimental tuberculosis in cattle, obtained by Nocard's method 

 of inoculation into the milk ducts), where the poisoning assumes 

 much greater importance. 



Among the bacterial diseases of man, leprosy may be cited as one 

 in which the intoxication is relegated to a subsidiary position, yielding 

 place to the mechanical substitution of the specific granuloma for the 

 normal tissues. It is only in the acute leprous exacerbations that we 

 perceive any signs of intoxication by the products of the leprosy 

 bacillus. 



All the instances cited, however, constitute but a feeble minority 

 which is completely thrown into the shade in the presence of very 

 numerous infections in which the toxic element dominates the situation. 

 Even in carbuncular diseases an exact analysis of their morbid phe- 

 nomena has compelled us to recognise the marked influence of the 

 [5J poison produced by the bacterium. The majority of the micro- 

 organisms act as poisoners which introduce themselves into the 

 organism where they can secrete toxins capable of provoking general 

 disorders of very diverse natures. Indeed in infective diseases a whole 

 gamut of very remarkable variations is produced. Thus many of the 

 micro-organisms capable of setting up septicaemias must multiply 



