30 
Proceedings of the Royal Irish Academy. 
could be destroyed by a sufficiently high temperature ;" also by the 
statement that rotten malaria cannot act like leaven, because fermen- 
tation is caused by the growth of the yeast plant. 
I^ow, the effect of the growth of parasitic plants in causing skin 
diseases is perfectly well known. I have shown, in my previous 
paper, how they may affect the lungs. JN'ext, that no putrefaction 
or conversion of matter can occur in prepared solutions, hermeti- 
cally sealed, was disputed by Pouchet, who adduced instances to the 
contrary, and has since been disputed by Drs. Bastiam and Prankland, 
with proofs present. Por myself, on opening the dense shell of a cocoa 
nut, and cutting through its oily albumen, I discovered in its milk a 
web-like plant — a kind of Achlya. I do not believe it probable that this 
Achlya got its germs " from the outer air, but regard it as an example 
of convertibility of matter — and correlation of beings— what some 
call rather wrongly spontaneous generation. Again, a dissection wound 
shows, in its results, how rotten matter may act with the quickness 
of leaven. I would prefer to call this theory the theory of motor 
change, rather than of motor decay. It yet remains to be proved that the 
facile explanation of the growth of the yeast plant being the cause of 
fermentation is true — or, being true, is the only true one. Two dif- 
ferent agents may produce the same effect. Gray Lussac and Liebig dis- 
believed its power. Pasteur, says Professor Tyndall, finally exploded 
their views of fermentation." I^evertheless, with due respect to both 
these distinguished men, I must believe that the yeast plant can have 
no retrospective action — that it cannot perform nor influence work done 
before its birth. J^ow, before the wort is made, and the yeast plant 
developed, molecular change has really already begun. Its effect is 
the difference between malt and raw grain. Starch has been altered 
into dextrine and sugar, without the yeast plant — which may or may 
not assist by its growth or by its decay (as some think) to continue the 
alteration until alcohol and vinegar be produced. In the castor oil and 
colza seeds, Fleury found that the fatty matter was converted into dex- 
trine and sugar, by fixation of oxygen — without, remark, the assistance 
of the yeast plant. Payen and Persoz believed the change to be owing 
to azotized diastase ; later observers have shown that it can be effected, 
under suitable circumstances, by any albuminoids, themselves being 
partially altered by the action of oxygen at a certain temperature, with 
moisture present. 'Eow, I have shown, in my previous paper that 
mucus particles — the excreta of man and animals — are present at times 
in the atmosphere — that a great increase of granules resembling exu- 
dation granules was present in the atmosphere of a patient seized with 
infantile remittent fever of a typhoid type. In these you have the 
requisite albuminoid substance present. And I am convinced that it 
depends on whether or not this or other albuminoids — animal and 
vegetable — be in a state of motor change, to furnish us or not with 
that contagious matter, whereby diseases are most commonly engen- 
dered and communicated. 
