29 
air of towns swarms with these germs to the amount of nearly two 
thousand to every cubic foot, while in pure country, mountain, or 
sea air, their presence can hardly be detected. The soil itself, to 
the distance of some feet below the surface, swarms with germs, 
and they are also found in the walls of ouz houses, the clothing we 
wear, the food we eat and the drink we consume, and even on our 
books and our money. I need hardly say that the great majority 
of these germs are, fortunately for mankind, of a comparatively 
harmless kind. 
It is suggested that to the presence of these micro-organisms in 
the air is possibly due the summer catarrh or hay fever, which is 
the result of some irritation of the mucous membrane of the nose 
and respiratory passages, and has hitherto been attributed to the 
pollen of grasses. 
The vitality of some germs, and especially of tle young spores, 
is very remarkable; thus tuberculous bacilli, found in the sputa of 
phthisical patients, which has been dried and kept for some months, 
are as capable of communicating infection as those which are 
quite fresh. Some of these spores are even capable, under favour- 
able circumstances, such as dry soil, &c., of retaining their vitality 
and virulence in a latent condition for enormously lengthy periods 
—for hundreds or even thousands of years; and may then under 
suitable conditions of heat and moisture break out into renewed 
life and power. Dr. Maljean has lately published an. account of 
some interesting experiments on germs discovered in the fluid 
collected from a wind instrument used some time previously by a 
phthisical musician. These germs were found to have fully re- 
tained their infectious properties. 
Heat is far more fatal to germs than cold, even if the latter be as 
low as the freezing point; whereas heat at boiling point (212 deg. 
Fahr.) kills any microbes with which we are at present acquainted. 
Next to heat, corrosive sublimate is the most effectual germicide we 
know, but owing to its highly poisonous character, either when 
used internally or upon a raw surface, it can only be sparingly 
used in cases of illness. Carbolic acid, which is also a caustic 
poison, is an effectual germicide, but less powerful than corrosive 
sublimate. Itis the poisonous nature of most germicides which 
prevents their internal use as remedies for those diseases due to the 
agency of microbes, for their action would be as fatal to the whole 
system as to the germs themselves. The most effectual method, 
therefore, of combating these poisonous germs is from without, and 
thus preventing their entrance as far as possible into the system. 
It is this principle which underlies the antiseptic treatment inaugu- 
rated by the celebrated Scotch surgeon, Sir Joseph Lister, which 
marks a new era in surgery, and has already been the means of 
