CAUSES OF DECAY AND DESTEUOTION OF TIMBER 257 
statement that any board that is cut and brought into the 
city from the forest is already covered with these fungi." 
It has been proved that the spores can be propagated by 
the saw of the workman if after cutting diseased timber he 
uses the tool on sound wood, and can even be carried on 
the clothes, and if, as German chemists tell us, four millions 
of these spores only occupy a cubic millimetre, we can 
easily judge of the risk of infection. As the human being 
brings with him from an infected neighbourhood the germs 
which in time produce typhoid and other diseases, so timber, 
brought from the forest, brings with it the spores of disease 
which only require a favourable situation to cause them to 
propagate and produce decay. These spores distributed by 
currents of air are what so quickly destroy the timber of 
dwelling-houses by what is familiarly known as " dry rot," 
although this is a misnomer, as will be shown ; and it 
should be the object of all users of timber to bring it into 
such a condition as to prevent the propagation of fungi and 
consequent decay. 
The chief " dry rot " fungus is known by the name of 
Meridius lacrymans, and recent German experiments have 
proved that it can propagate itself either by mycelia or 
spores, but principally by the latter. 
Moisture and a certain amount of heat are indisj)ensable 
conditions for decay of timber. Without moisture no 
growth of fungus can take place. Temperatures between 
60° and 100" Fahr. appear most conducive to fungus life, 
it will not exist at freezing point, and in higher tempera- 
tures than above given appears to lose its vitality. 
Mr. Eichard Falck, in a recent paper in the Zeitsclirift 
fill- Hygiene, Leipsic, has pointed out that he has been able 
to prove that warmth is fatal to the growth of dry rot 
fungus, and that in houses attacked it is possible to destroy 
it entirely by heating the air to 38° C. (100° Fahr.) for four 
T. s 
