16— SANITARY PRIVY. 
(4) Experience shows that it is exceptional that the excrement is 
properly covered with dry earth or lime; hence the system is not 
so efficient as is popularly supposed, 
(5) Neither dry earth nor lime, in practical usage, can be relied 
upon to destroy all disease germs which may be in the excreta; hence 
their use is likely to give rise to a false sense of security in the public 
mind. 
(6) If the dejecta at the time of burial contain fly grubs these 
larve may crawl through the earth to the surface, where they can 
complete their development into adult flies and spread infection 
from the buried night soil. ; 
Privies of the “dry system” should not be marked more than 
75 points on a scale of 100. 
Figures 6 and 7 (pages 22 and 23) represent an SUE which 
may te used as a dry privy. 
THE “ WET SYSTEM.” 
In the “ wet-system ” privies some fluid is used in the receptacle 
either (1) to disinfect the excreta, or (2) to act as an Insect repel- 
lent, or (3) to increase the destruction of disease germs in the ex- 
creta by natural fermentation. Figures 6 and 7 represent outhouses 
which can be used as “ wet-system ” privies. 
The advantages of the “wet system,’ when applied to outhouses 
shown in figures 6 and 7, are 
(1) It decreases the ue maaiaee of the privy contents. 
(2) It is cheap. 
(8) It greatly decreases the chances of spread of infection by 
flies because they can not breed in the excreta; hence rigid fly screen- 
ing is not so necessary. 
(4) It kills or renders harmless a considerable proportion of cer- 
tain infections contained in the excreta. 
(5) Its efficiency does not depend upon the intelligence or coopera- 
tion of all persons using: it. 
The disadvantages of the 
shown in figures 6 and 7, are: 
(1) It is more difficult to keep clean than the “dry system,” be- 
cause of the danger of soiling the floor when the receptacie is emptied. 
(2) Unless the receptacle is very deep there is likely to be more or 
less splashing. 
(3) The labor and frequency of cleaning are about the same as in 
the case of the “dry system.” 
If the wet system is used it is best to fill the receptacle about one- 
fourth full of water, on the surface of which a cup of petroleum 
is poured. The petroleum acts as an insect: repellent. 
463 
“wet system,” as applied to outhouses 
