i68 INFECTIOUS AND PARASITIC DISEASES. 



in this sense all infectious diseases are not inoculable, 

 that is to say, whether the entrance of the agent does not 

 depend upon some defect created in the integument or 

 mucous membrane by another cause. Neither the 

 nature of the infectious agent nor the region of the body 

 which is the primary site of the disease enter into the 

 discussion; nor is it disputed that penetration must 

 occur; the question is, how does it happen, whether 

 through the action of the bacteria themselves, or through 

 the agency of another cause? If an accessory cause 

 paves the way in all infections by interrupting the con- 

 tinuity of a surface, then all infectious diseases are inoc- 

 ulable. This latter belief, it will be recalled, is in 

 entire accord with views previously expressed in the 

 chapter on "The Phenomena of Infection," particularly 

 in that portion which treats of the part the body plays 

 in its production. 



The lesions of entrance in some diseases are more 

 palpable than they are in others, and in others again, 

 they can never be found; yet that this latter fact is not 

 a safe argument to use against the inoculability of a 

 disease will be seen from a few illustrations. Take, 

 for example, such a disease as yellow fever. Before 

 the epochal work of the medical officers of the U. S. 

 Army in Cuba, during 1898-99, yellow fever was 

 regarded as a highly contagious disease, to guard 

 against which it was deemed necessary not only to 

 subject exposed individuals to the most rigid quarantine. 



