692 MICROBIOLOGY OF THE DISEASES OF MAN AND ANIMALS. 



diphtheritic patient coughs into an attendant's face; or mucous membranes 

 may be applied to skin or vice versa, as in the kissing of a chickenpox 

 patient; but in general the discharges are conveyed somewhat indirectly. 

 The prime route from mucous membrane to mucous membrane is fur- 

 nished by the hands. An attendant touches the patient's lips or wipes 

 out the mouth or otherwise performs toilet services and receives the dis- 

 charges upon his fingers. The fingers go then to the attendant's mouth 

 directly, or touch something (the tines of a fork or the bowl of a spoon, 

 etc.) which in turn goes into his mouth; or the attendant may touch the 

 fork or spoon or food of others and thus they become infected. He may 

 milk a cow and so get the discharges into the milk. With the infection 

 in his own mouth he may kiss others and transfer it to them. It is 

 impossible to outline the infinite combinations that may occur, but the 

 principles are here made obvious. When the infective discharges handled 

 are those of the bladder or bowel (as in typhoid fever, cholera, etc.) the 

 same dangers of transmission are encountered and unfortunately too often 

 realized. The wholesale discharge of sewage into water supplies is 

 merely a gross example of the same principle of transfer of discharges 

 from human bodies to the human mouth. 



Another factor in the transmission of disease (as distinguished from 

 the transmission of the germ) is the condition of the infectee. The germ 

 is analogous to a seed; the methods of transmission are somewhat 

 analogous to the distribution of seeds in nature; the condition of the 

 infectee is analogous to the character and nutritional condition of the 

 soil which the seed reaches. 



If for any reason the germ will not develop in the soil where it is 

 planted, or, still further, if it grows but fails to produce those poisons 

 through which alone it acts, or finally if, growing and producing its 

 poisons, the soil neutralizes the poisons, no disease results. Science, 

 logic, and the law (each of which regards itself, and rightly so, as merely 

 an apotheosis in its own line of "common sense") unite in the dictum 

 that a disease exists only when the normal functions of the body are in 

 some way interfered with to the detriment of the body. The mere infec- 

 tion of the body with a disease germ does not, in science, logic, or the law, 

 constitute disease. Hence, the reception of a disease germ into the 

 body is but the first of three essentials, the other two being poison-produc- 

 tion by the germ and poison-action on the tissues. Many persons are 

 insusceptible to the poisons of one or more disease germs. In whatever 



