CXXlil 
results at present, in the absence of knowledge as to what are dangerous 
or harmless forms. 
CONNECTION BETWEEN IMPURE WATER SUPPLY AND SPREAD OF DISEASE. 
Typhoid fever is spread by the contamination of water or air by a 
specific poison derived from the discharges of infected persons, and 
there is little doubt that this poison consists of living germs, although 
they have not yet been absolutely identified. The disease may be due to— 
1. Percolation of liquids containing these germs, sometimes to a 
considerable distance, through the soil into wells and springs or 
underground tanks, or discharge of sewage into rivers. 
2, Exhalations fronrill-trapped closets, perhaps connected with house 
cisterus, defective sewers and privies, etc., containing germs 
derived from patients; water or milk stored in the immediate 
vicinity may in this way be rendered dangercus. When exhala- 
tions issue into the air they are stated to be immeasurably more 
likely to communicate disease than is the atmosphere which im- 
mediately surrounds fever patients. 
3, Contaminationof milk, and alsopossibly of spirits, by admixture 
with germ-polluted water ; the disease is said to have been spread 
in one case at least by the use of bad water for washing the 
milk-cans. The popular belief in the absolute protective action of 
spirits, even in immoderate proportion, is a dangerous delusion. 
The following cases of the spread of typhoid fever by water are 
instructive, and can scarcely be too frequently quoted :— 
1, Three hundred and fifty-two persons suffered from typhoid fever, 
the cause being conclusively proved to be the accidental addition 
to the water of a small amount of excrement from asick man 
who worked fora time in the deep wells supplying otherwise pure 
water to a large district. Such minute admixture would defy 
detection by chemical or any other means known at present. 
2. A case of typhoid fever occurred in a cottage on the banks of a Swiss 
mountain stream, which below the cottage flowed for some 
distance underground ; the water, etc., taking two to three hours 
to reach a village some distance lower down, the cour-e and rate 
of flow being ascertained by throwing in opposite the cuttage about 
a ton of salt. A still larger quantity of flour was afterwards 
thrown in and well mixed with the water ; none of it reached the 
village, showing that tolerably efficient filtration, which entirely 
stopped the flour, allowed the germs of typboid to pass in suffi- 
cient quantity to communicate the disease to 17 per cent. of 
the population. 
3. The town of Croydon was supplied with water obtained from deep 
wells sunk inside the town ; these were lined with iron cylinders 
for a certain distance from the surface to shut out the subsoil 
water which was knosvn to communicate more or less with the 
sewers; water from the wells was frequently analysed, but no 
results pointing to defilement could be obtained until the level 
was lowered by pumping, and samples of the water trickling 
through the sides of the wells collected and examined, the 
movement of the subsoil water being also traced by chemical 
means. Undoubted sewage contamination was discovered, a 
sufficient reason for the fact that one person in 42 living in 
the Croydon water district suffered from typhoid fever, as com- 
pared with one in 809 in the district immediately outside, 
although in many cases the same sewers were used in common 
by the two districts. The well yielded 0°04 part, and three 
samples of the leakage 0°14, 0:26, 0:22 parts of albuminoid 
ammonia per million. 
