CHAPTER II] 

 DISEASES COMMUNICABLE IN MILK 



Wherever men have been living together, destruction by pestilence 

 has been going on. Of the nature of this mysterious foe man could but 

 speculate in bewildered terror. The savage thought the sick possessed 

 of demons; among more advanced peoples the religious looked on afflic- 

 tions of this sort as visitations from God for sin. Slowly with the emerg- 

 ing of medicine from empiricism to a science, more materialistic explana- 

 tions were advanced and belief in the supernatural gave way. In the 

 period from 1815 to 1835 the achromatic objective was invented and the 

 compound microscope perfected so that man had a new weapon at his 

 disposal, one that made the enemy visible. From this time on rapid 

 progress was made in the acquisition of exact knowledge concerning 

 contagion. Discoveries in microbiology led to the isolation of the specific 

 germs of diseases so that it was possible to interpret observations that 

 were made on the mode of transmission of these maladies more accurately, 

 but prevailing ideas had to be abandoned or considerably changed before 

 the truth was reached. In the latter part of the 19th century the filth 

 theory of disease obtained wide credence; it was briefly that disease germs 

 were created out of filth or decomposing matter. Practically, it led to 

 the cleaning up of many foul places but it did not prove sound and only 

 in a greatly modified form is it now applied, yet testimony of the hold it 

 took is to be found in the fact that even now the public has faith in pro- 

 tective health measures that have nothing besides this outgrown theory 

 to recommend them. As this conception of the way in which contagion 

 is engendered was given up, there was substituted the belief that it was the 

 offspring of environment; and air, food, water and clothing were looked 

 upon as being the sources whence it sprang. This proved to be only a 

 part of the truth for it has been found that it is exceptional for the virus 

 of disease to remain long alive in these things and within the last decade 

 their importance as sources of contagion have been minimized. It is 

 now believed that the body itself is the fountain head of infection. It is 

 the various discharges of the organism that are dangerous and the study 

 of outbreaks of contagion is largely a study of the way saliva, urine, feces 

 and other excretions are circulated in the affected community. To a less 

 extent man is infected by animals and through the bites of insects but 

 even so the morbific principle is transferred by a more or less direct route 

 from the sick to the well. It is the ailing beast or man that is the poten- 



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