YELLOW FEVER. 691 



patient, but they do so in articles about him (fomites) ; germs may 

 be carried in clothes and other articles, or in ships, especially in 

 the bilge- water. These germs are deprived of activity by a freez- 

 ing temperature, but may be awakened by a heat of 90 Fahr. ; 

 they are destroyed at 250 Fahr. 



It has been maintained that yellow fever is only a variety of 

 malarial fever, but the evidence seems to be very strongly against 

 this view. 



The National Board of Health (United States, 1879) reaches 

 conclusions about as follows : 



The essential cause of yellow fever is a " germ " which is capa- 

 ble of growth and propagation outside of the human body, and 

 which flourishes especially in decaying organic matter. Disinfec- 

 tion must attack the germ and that on which it grows. Disinfec- 

 tion is a poor substitute for cleanliness ; it is best done by sulphate 

 of iron, carbolic acid, fresh quicklime, fresh charcoal-powder, chlo- 

 rides of zinc and aluminium, and permanganate of potash. The 

 disinfectant must be brought into actual contact with the germ ; 

 when the germ is dry, it must be moistened or else subjected to a 

 dry heat of 250 Fahr. While the infected articles are dry, move 

 them as little as possible ; moisten them with boiling water or 

 some disinfectant solution. The Board advises moist cleansing, 

 followed by fumes of sulphur, using about 18 ounces of sulphur 

 to 1,000 cubic feet of the space to be disinfected. The removal of 

 an unpleasant odor is no proof of disinfection. Textile fabrics 

 which have been exposed to yellow-fever infection should be placed 

 in boiling water or in an oven ; rooms and houses which have been 

 occupied by yellow-fever patients should be disinfected as soon as 

 possible. Lastly, they suggest that " every suspicious case of sick- 

 ness should be at once isolated, and every possible precaution taken 

 to prevent infection, by providing attendants who have had the 

 disease, and thorough disinfection of all discharges from the sick. 

 If the disease proves to be yellow fever, all articles of clothing and 

 bedding used about the sick should be burned, the house should be 

 vacated, and every room tightly closed and fumigated with burning 

 sulphur." 



Yellow fever only occurs when the temperature is high ; in the 

 northern part of the United States most of the epidemics have be- 

 gun in July and August. A frost suddenly checks the spread of 

 the disease. 



Susceptibility to this affection is greatly influenced by race and 

 acclimation ; in many epidemics negroes escape ; acclimation may 



