GERM-THEORY OF DISEASE. 349 
majority of the spores of Schizophytes which are also found. Michel 
has calculated that in the neighbourhood of the observatory at 
Montsouris a man may inspire in 24 hours 300,000 mould spores 
and 2,500 Schizophytes. Probably not j,th of these are possessed 
of any life or capacity for further development, but Michel has 
nevertheless discovered that the curve representing the occurrence 
of Schizophytes in the atmosphere, and the curve representing the 
prevalence of infectious diseases, are coincident. He has shown the 
necessity for ventilation by pointing out the great increase of 
microbes in the atmosphere of the Parisian hospitals during winter, 
when doors and windows are kept close for warmth’s sake. He has 
also shown that microbes are not more abundant in the neighbourhood 
of open sewers than in the air generally, a fact which is confirmed by 
investigations of Hansen and Naegeli. The latter demonstrates that 
all micro-organisms must be previously dried before being carried 
into the atmosphere. They exist there generally in the spore- 
condition, a condition which usually steps in when changes unfav- 
ourable to the ordinary method of propagation by division have come 
into operation. The spores, which are produced in the interior of 
the cells of the Schizophytes, are possessed of much greater vitality 
than the mother-plants, being able to resist extremes of temperature, 
and deprivation of moisture and food immeasurably better than 
these. The discovery of such spores and their properties has given 
a death-blow to the doctrine of spontaneous generation, for it is now 
satisfactorily determined that any organic infusion may be kept per- 
fectly free from micro-organisms in a sealed flask, if the proper 
precautions have been taken not only to kill the mature Schizophyte 
in it, but also their spores. 
It is not surprising in view of these facts that the strength of the 
disinfectants used to kill septic material must be very different 
according as the material is in a vegetating or spore-condition. In 
the latter case no volatile antiseptics, except chlorine and bromine, 
have been found to possess any efficacy, and it has been shown 
that the antiseptic virtues of carbolic, salicylie, &c., have been 
greatly overestimated. As a result of various experiments made to 
determine the best means of disinfecting clothes (rags impregnated 
with spores of Bacillus anthracis being chiefly employed), prolonged 
boiling—for several hours—has been recognized as the simplest effi- 
cacious method. The experiments have shown that the process of 
