Mourad, Auge 1, 1870. of the Atmosphere. 97 
not be seen for want of motes. Within doors, at a country place, 
in winter and spring, the motes were plenty, and the sunbeam well 
defined. Out of doors, in a calm spot, I could see the bright slit 
where the ray entered the arbour. I could see the bright spot on 
the floor where it fell; but between these two visible points there 
was no visible line. It was impossible to say where the ray was, 
until the hand was placed in its way, or a little dust shaken through 
it. The dust then produced patches of light in the invisible ray, 
just as Professor Tyndall caused patches of stellar darkness by 
expelling the dust from the visible ray. 
4th. The “germ theory” asserts “that epidemic diseases are 
due to germs which float in the atmosphere, enter the body, and 
produce disturbance by the development within the body of para- 
sitic life.” It is opposed to the opinion that epidemic diseases are 
propagated by a kind of malaria, which consists of organic matter 
in a state of motor-decay. It is supposed to be supported by cer- 
tain statements about the non-occurrence of putrefactive changes in 
closed vessels, which have been disputed ; and by the statement that 
rotten malaria cannot act like leaven, because fermentation is caused 
by the growth of the yeast-plant. Now, the effect of the growth 
of parasitic plants in causing skin diseases is well known; if they 
caused epidemics likewise, their presence would, in all probability, 
have been as soon detected. Pouchet, and recently Dr. Bastian, 
dispute Pasteur’s views. The author of this paper, having opened 
the dense shell of a cocoa-nut, and cut through its oily albumen 
(both perfectly intact to all seeming), found in the milk a web-like 
plant, a kind of Achlya. I do not believe it probable that it got 
its “germs” from the air, but regard it as an example of the con- 
vertibility of matter—and correlation of beings—rather wrongly 
called by some spontaneous generation. [If it got its germs from 
the air, then far more readily could the air in the pleura get germs 
from the outer air, in Professor Lister's sample case. For if the 
dense tissues of the cocoa-nut coverings could not filter out the 
germs, neither could they be kept out of the pleura-cavities. 
Microphytes have been found in eggs, and mould in the brain of 
the golden pheasant.| Again, a dissection wound shows, in its 
results, how rotten matter may act with the quickness of leaven. 
However, this theory should be called the theory of motor-change, 
rather than of motor-decay. It yet remains to be proved that the 
facile explanation of fermentation by the growth of the yeast-plant 
is true—or being true, is the only true one. ‘Two distinct agencies 
might cause an identical effect. Gay-Lussac and Liebig disbelieved 
in it. Pasteur, says Professor Tyndall, finally exploded their views 
of fermentation. Nevertheless, with very sincere respect for both 
these distinguished men, I must believe that the yeast-plant can 
have no retrospective action, that it cannot influence work done 
