292 
On the Cultivated Potato. 
potatoes have deteriorated in their disease-resisting powers : a 
variety from seed takes four to six years for its real establish- 
ment, and then under the most favourable circumstances a good 
variety might be expected to degenerate in twenty years : the 
production of new varieties is of national importance. 
Six millions of money, according to the Registrar-General, 
eight millions, according to Professor Baldwin, was the loss 
from potato-disease in Ireland alone in the one year preceding 
the inquiry, namely in 1879. It is impossible here to sum up the 
interesting evidence ; it should be studied, and students must 
draw their own conclusions. There are, however, a few points 
on which I would touch lightly: the biography of the potato- 
mould or fungus is treated exhaustively ; it is of its kind 
similar to the common mould which attacks damp and decaying 
vegetable substances : the potato-mould differs in inflicting 
mortal injuries on a living plant. If you take plants and 
animals generallv, you never find parasitical growth in a per- 
fectly healthy condition ; throughout the whole of nature para- 
sitical growth attacks the feeble. Ravages are due to sudden 
climatic conditions fitted for the germination of the hovering 
and omnipresent seeds or spores : all epidemics are subject to 
sudden acceleration. The potato "murrain" is compared to 
blood-poisoning in animals, and the analogy holds :* Given the 
condition to invite the growth of mould, be it a cheese or be it a 
potato, there, hovering, are the spores or seeds, and they are 
In his opinion, the principal mischief in the case of the potato, as in other culti- 
vated plants, arises from the fact that we grow in great masses species that in 
nature are scattered alx)ut in different habitations." 
* Darwin observes (' Origin of Species ') : " .\nalogy mav be deceitful — yet all 
living things have much in common: chemical, cellular, laws of growth, liability 
to disease and injury." " Living bacteria," says Bealo (' On tlie Microscope,' 
5th Ed., 1880), "originate in decomposing matters .... living bacteria, like 
other living things, come from germs formed by pre-existing living things like 
themselves." " Bacteria," says Hogg (' On the Microscope,' last Ed., p. 749), 
" with omnipresent spores produce ferments in the animal body .... splenic 
fever, for example, attacks horses, cattle, sheep, rodents, and even man ; bacteria 
multiply to swam in the blood, and in a few hours death supervenes." Dr. 
Koch, Chief of the German Cholera Commission, reports, under date, Jan. 7th 
inst. Somt-tbing like the discovery of specific cholera bacilli — "If," says the 
doctor, " bacilli of a specific character are exclusively incident to the process of 
cholera, the original connection between tlie appearance of these b.icteria and 
the disease would scarcely admit of any doubt.' — ['Times,' Feb. 16, 1884.] 
" The discover)- by Dr. Koch and his colleague.^, of cholera bacilli in a tank in 
the Baliaghatta suburb of Calcutta, which has already been telegraphed to the 
' Times,' has excited much iuterest here, and is ckariy a great step forward in 
medical science. The chain of evidence, however, connecting these bacilli with 
the cause of the disease is not j'et complete. The Geiman doctors have proved 
that this organism exists in all cases of cholera, but in no other disease: that it 
has been found in a tank used by the people among whom the diseasfl appeared, 
and that it diminished in numbers as the disease died away. But they liave still 
to show whether the bacillus is the cause or the result of cholera." — 'Times," 
Feb. 25. 
