CHAPTER IV. 



GENERAL CONSIDERATIONS OF THE RELATION OF 

 BACTERIAL POISONS TO INFECTIOUS DISEASES. 



THE majority of diseases may be grouped from an etio- 

 Jogical standpoint into the following classes : (1) Trau- 

 matic ; (2) infectious ; (3) autogenous ; and (4) neurotic. It 

 must be understood, however, that in many diseases the 

 cause is not single, but multiple, and for this reason sharp 

 lines of classification cannot be drawn. For instance, the 

 greatest danger in those traumatic affections in which the 

 traumatism itself does not cause death, lies in infection. 

 The wound has simply provided a suitable point of en- 

 trance for the infecting agent. Indeed, the break in the 

 continuity of tissue may be so slight that it is of import 

 and danger only on account of the coincident infection. 

 This is true in many cases of tetanus. Furthermore, an 

 infectious disease, whether it originates in a traumatism or 

 not, is markedly influenced by what we are pleased to call 

 the idiosyncrasy of the patient, and by which we mean the 

 peculiarities of tissue metabolism taking place in the indi- 

 vidual at the time. A dozen men may be exposed alike to 

 the same infection, and the infecting agent may find a suit- 

 able soil for its growth and development in two of these, 

 while in the other ten this same agent meets with such 

 adverse influences that it dies without producing any appre- 

 ciable effects ; or all may be infected, but with difference in 

 degree, as is evidenced by variation in symptoms, in the 

 length of time that this infecting agent continues to grow 

 and develop in the body and in the ultimate result. Every 

 physician who has had experience in the treatment of 

 typhoid fever, diphtheria, scarlet fever, or, in short, of any 

 of the infectious diseases, will appreciate the importance of 

 the personal equation in his patients. 



