C02sTKUL ()!• UACTEIUAJ. DISEASES 237 



by angry gods, demons, and witches; next, b}' the air as 

 miasms and eflhivia; then, by fomites in dust of clothmg or 

 merc'liandise ; and, iiiially, we liave come down to the sure 

 exidence ot" science that contact infection, chiefly by tlic 

 liands, accounts for ahnost all the spread of common diseases, 

 and insects, by contacit or inoculation, for most of the rest. 



Air not an important carrier. Just now the air is rapidly 

 losing all its terrors, smallpox being the only disease which 

 may possibly, though not probably, be carried from house to 

 house by this agency. (This does not mean that hisects that 

 Wy may not transmit many infections by contact.) Cha})in 

 puts the case carefully and sensibly as follows : 



Only a lew authorities now assert tliat disease is carried liv tlir 

 atmosphere outside of dwellings, and this assertion is made only in 

 regard to smalliwx. . . . Infection hy air, if it does take place, as is 

 commonly believed, is so ditficnlt to avoid or guard against, and so 

 universal in its action, that it discourages effort to avoid other sources 

 of danger. If the sick-room is jfilled with floating contagium, of what 

 use is it to nuike much of an effort to guard against contact infection? 

 Jf it should })rove, as T firmly believe, that contact infection is the chief 

 way in which the contagi(JUs diseases spread, an exaggerated idea of 

 the im})ortance of air-borne infection is most mischi<'V(Mis. It is impos- 

 sible, as I know from experience, to teach people to avoid contact in- 

 fection while thi'v are tirmlv convinced that the air is the chief vehicle 

 of infection. . . . Without denying the i>ossibility of such infection, it 

 may be fairly affirmed that there is no evidence that it is an a}»preciable 

 factor in the maintenance of most of our common contagious diseases. 

 Wt' arc warranted, then, in discarding it as a working hypotliesis ami 

 <levoting our chief attention to the prevention of contact infection, li 

 will be a great relief to most persons to be freed from the sjiectei- of 

 infectc<l air — a specter which has pursued the race from the time of 

 IIij)pocrates ; and we may rest assured that if people can as a conse- 

 (juence be better taught to ])ractice strict personal cleanliness, the}' 

 will ])e led to do that which will, more than anything else, prevent 

 aerial infection also, if that should in the end be proved to be of 

 more importance than now appears. — Chaim.x, "Sources and Modes 

 of Infection." p. 'JC:; ff. 



