538 On the Nature and Causes of the Decay in Potatoes. 
food. The mode of growth of fungi favours this opinion, for they 
throw out abundance of small filaments which might be called 
their spawn, and these insinuate themselves everywhere through the 
cellular tissue, destroying its contiguity, and allowing the various 
constituents of the tuber to mis together and enter into decay. It 
was argued that analogy confirmed this opinion, for there were 
many points of similarity in the disease to the decay of" apples, 
which, it was contended, Hassal and others had proved to be due 
to fungi. It was undoubted that both the spawn, the fungi them- 
selves, and their germs, could be detected in abundance in the 
diseased potato, just as they can be in a rotten apple ; and, there- 
fore, supposing them to be the true cause of rot in the apple, it 
was fair to accept this as the explanation in the case of the potato. 
But then chemists had always contended that rot or decay was a 
true chemical phenomenon, quite independent of fungi, which 
came there because in the rotten matter they found a soil suited to 
their growth. Decay, said the chemist, is merely a kind of slow 
burning of the tissue of the organic substance — a union of it with 
the oxygen of the air, while putrefaction is a rapid change pro- 
duced by the progress of the decay when the supply of air is in- 
sufficient. It was of the utmost importance to determine which 
theory is correct, for upon this must be founded our plans for 
treatment. 
Those who insisted upon the fungous origin of the disease had 
good grounds to fight upon ; and, headed by Morren, have drawn 
up in very imposing battle array. Their arguments are very in- 
genious, and deserve the most careful attention. 
Reasoning upon our assertion that decay is a union of oxygen 
with the organic matter of the tissue, they take an apple or a 
potato and cut a slice from it, so as to expose a large surface to 
oxygen ; but the potato does not decay, and they employ this 
experiment as an argument for their view. They then bruise the 
surface of an apple, making only a very small puncture to admit 
the germs of the fungi, and this apple, although not nearly so 
freely exposed to the air as in the other case, rapidly becomes 
rotten and covered with fungi. But these experiments are by 
no means conclusive. Thus when the a])ple or potato was <:ut, 
the clean incision had indeed cut up some of the cells and mixed 
a little of the juices upon the surface, but these soon dried, and 
were put beyond the attack of decay, which requires the presence 
of moisture. In the other case, where the apple had been bruised 
and the skin slightly perforated, the cells had become ruptured, 
the gluten and albumen, which are the first to decay, became 
freed from the control of vitality, and mixed with the sugar and 
other matters, moisture remained, and air was admitted under all . 
the circumstances most favourable to the rapid progress of decay. 
