350 GERM-THEORY OF DISEASE. 
disinfection of rooms, clothes, &c., during and after contagious disease 
ought to be under the control of a health officer, in order that this, 
the most important method of combating the spread of contagious 
diseases, should be efficiently and systematically carried out. 
The introduction of an abundant supply of pure water, and the 
construction of proper drainage systems, are now aimed at by most 
large cities: in many the compulsory use of these by all the inhabi- 
tants remains to be carried out. So much knowledge has been 
acquired as to the origin of disease in course of the researches 
alluded to in the previous pages, that it becomes the obvious duty of 
educators to extend and provide for the increase of that knowledge. 
This can be most efficiently done by giving every medical student an 
opportunity of becoming practically acquainted with the methods of 
research which have been adopted in the enquiries referred to. It 
is obvious that medical men in practice will rarely combine leisure, 
inclination and capacity for such studies ; but, on the other hand, 
much hard work has been expended with little or no result, simply 
from a want of rigid early training. Such is particularly necessary 
in the study of these lowest organisms, where errors of observation 
and experiment are avoided with the greatest difficulty. 
