220 INFECTION AND IMMUNITY 



usually twelve days and the duration of the disease in 

 cases ending in recovery is about three weeks. That 

 the smallpox virus may be carried a considerable dis- 

 tance through the air by currents of wind, and the 

 disease thus be propagated, seems to be well estab- 

 lished by the observations of certain English authori- 

 ties upon the subject. But it is not certain whether 

 it is directly, as dust carried by the wind, or indirectly, 

 attached to the feet of flies which have been in con- 

 tact with the pustules on the body of a smallpox pa- 

 tient, that the disease has been conveyed in the 

 instances which have been recorded. The extreme 

 limit to which the disease is likely to be commun- 

 icated in this way probably does not exceed a mile. 

 The disinfection of the room occupied by a small- 

 pox patient, and all its contents, calls for the most 

 careful, intelligent, and thorough measures. Only 

 absolutely necessary articles should be left in the room 

 and it is well to have screens in the windows to exclude 

 flies. Abundant ventilation is important. While oc- 

 cupied by the patient, floors, window-ledges, and all 

 places where dust is liable to accumulate should be 

 frequently wiped with a cloth wet with a suitable dis- 

 infecting solution (5 % solution of carbolic acid or 

 i : 1000 solution of corrosive sublimate). All washable 

 articles which have been in contact with the sick per- 

 son or in use in the sick-room should be immersed in 



