86 TEE POPULAR SCIENCE MONTHLY 



THE TRANSMISSION" OF DISEASE BY MONEY 



By A. CRESSY MORRISON 



CHICAGO, ILL. 



THE demonstration of a few of the avenues by which infection is 

 transmitted is among the triumphs of modern experimental 

 medicine. By its revelations cholera is now known to be mainly a 

 water-borne disease ; likewise it is recognized that typhoid is transmitted 

 by those means by which the waste products of an infected individual 

 are transferred either directly or in round-about ways to the food of an- 

 other; malaria is no longer thought to be wafted by the night air, but is 

 known to be directly carried to and introduced into the system by the 

 mosquitoes; and, even a later triumph, yellow fever is seen to approach 

 its human victim through the same hosts; while, finally, it has been 

 determined that bubonic plague, the scourge of the tropical east, is 

 carried by the rat flea. Notwithstanding these recognized avenues of 

 transmission in specific instances, many other and more common infec- 

 tions continue to travel from one to another by paths that we do not 

 know. 



Before the knowledge of cholera transmission by water, it would 

 have been considered a scientific contribution to the subject to have 

 demonstrated the absence of cholera germs in twenty-four samples of 

 water taken at random some of which perhaps were dirty; but to-day 

 we know that the bacteriological study of water for evidence of cholera 

 will usually demonstrate the avenue of infection only when and where 

 cholera is prevalent. Similarly, it would be a matter of the greatest 

 surprise if the examinations of twenty-four or many more samples of 

 water or food for typhoid germs revealed their presence, even if the 

 water or food was dirty and offensive. Likewise, the most diligent 

 search of twenty-four or more mosquitoes for malaria or yellow fever 

 would in all probability fail to show a single malarial plasmodium or 

 yellow fever bacillus. In the same way, hundreds of rat fleas might be 

 caught and made to bite guinea-pigs or rats without the production of 

 bubonic plague in a single instance. Do any of these negative observa- 

 tions disprove or discredit in the least degree our present views on the 

 origin of the various diseases whose avenues of infection we have 

 mentioned ? 



By what privilege then does our scientific friend, Warren W. Hil- 

 ditch, of the Sheffield Laboratory of Bacteriology and Hygiene, Yale 

 University, claim in The Popular Science Monthly of August, 1908, 

 even the least knowledge of the transmission of disease by money from 

 the bacteriological study of twenty-four bills, " the dirtiest I could ob- 

 tain from various sources, such as railroad, trolley and theater ticket 



