SIXTEENTH ORDINARY MEETING. 217 
has been assumed cause malaria are all much less satisfactory than 
the germ theory, in which some bacterial organism, e. g., Bacillus 
Malarie, is supposed to be the immediate cause, Dr. Bryce went into 
a discussion of how the local physical conditions might favour the free 
development of these germs, as it is well known that vegetable organic 
matter in a decaying state forms a favourite nidus for the development 
of bacteria of every kind. This material is largely present in some of 
the overflowed lands along the river, but free development of organic 
life in such depends upon the amount of water present in the soil. 
This necessarily varies with the dryness of the season and with the 
height of the river-water. This last point introduced the subject of 
its probable effects upon the ground-water of the low lands along the 
river. Through the denuded nature of the river-valley, the subsoil water 
of the neighboring higher lands naturally drain toward the valley along 
impervious beds of clay, and in some parts along the surface of the 
underlying rocks. ‘This is seen in some parts in the presence of flow- 
ing wells. But, according t> Miquel’s experiments, it is not enough 
for the prevalence of germs in the air that they be developed in the 
soil. Itis necessary that the upper layers of soil dry out sufficiently 
to allow the winds to carry these freely into the air. Further, their 
free development in the soil depends largely upon the amount of air 
in the soil, or oxygen. This it is clear must vary with the height of 
the ground-water, since as the water rises or falls the air must be less 
or more in the interstices of the soil. Hence, though ground-water 
conditions the amount of air in the soil, it is after all the oxygen of 
the air which determines the development of germs. But the next 
point in this connection is the fact that, as the temperature of the 
soil varies greatly from that of the contiguous atmosphere, especially 
during the warm summer weather, it follows that there is a regular 
circulation of ground air, new oxygen being constantly taken into the 
soil to supply the conditions of free zymotic development; and fur- 
ther, that this circulation probably serves to some extent as a vehicle 
for carrying the germs of the soil into the air. Upward currents of 
air during the day prevent an accumulation of atmospheric particles 
near the earth, and, on the other hand, the upper colder strata of air 
descending toward and after sundown, and especially in calm weather, 
cause accumulations near the earth of germs which have been carried 
up during the day. Hence, along with the increased humidity, 
is probably explained why night air is proportionately more mala- 
