124 
trial processes advantage was taken of 
‘spontaneous’ changes of highly peculiar 
and unexplained characteristics. 
Contemporary spontaneous generation, in the 
first half of our century, was commonly ac- 
cepted as a fact even by many scientific 
men, who held that it was the simplest ex- 
planation of the origin of the swarms of 
microscopic organisms observed in putre- 
fying liquids or infusion. The belief in 
easy and constant spontaneous generation 
of living from lifeless matter is probably as 
old as the human race, and if we bear in 
mind the ignorance which was universal 
concerning the nature and complexity of 
even the simplest forms of life, and the 
complete lack of trustworthy evidence such 
as we have to-day against the theory of 
present-day abiogenesis, we can not wonder 
that this theory should have been so re- 
cently and so widely held. It is true that 
some of the most acute observers, such as 
Leeuwenhoek, had utterly refused to ac- 
cept the theory, arguing that the total ab- 
sence of abiogenesis in the higher forms of 
life made its occurrence in the lowest forms 
highly improbable, but we must admit that 
in these cases their conclusions were based 
rather upon instinct than scientific evi- 
dence. Granting, as we must, the theo- 
retical possibility, and perhaps probability, 
of this process in the primordial origin of 
life upon our globe, we may well be slow to 
condemn those who leaned toward the the- 
ory of modern spontaneous generation as 
the most reasonable explanation of the my- 
riad life of to-day in the under microscopic 
world. At the same time it can hardly be 
doubted that the belief in present-day spon- 
taneous generation represented the last sur- 
vival of such traces of belief in magic, al- 
chemy, and the transmutation of metals, as 
the nineteenth century inherited from its 
predecessors. 
In the early part of our century there 
was a group of natural phenomena of a 
SCIENCE. 
(N.S. Vou. XIII. No. 317. 
different order, which, though painfully 
familiar, was equally puzzling and myste- 
rious. Seemingly spontaneous in origin, 
always inexplicable, erratic and mysterious 
in transmission, often swift in operation 
and fatally destructive to human life, the 
mysterivuus phenomena known as epidemics, 
plagues and pestilences were among the most 
dreaded of all natural occurrences. Many 
indeed still spoke of them as ‘ visitations 
of the Almighty,’ and treated them as if 
they were of superhuman origin, but Dr. 
William Farr, in preparing a classification 
of diseases for the purposes of the registra- 
tion of vital statistics—made for the first 
time in history on a large scale in England 
in 1839—recorded epidemics, plagues and 
pestilences as strictly natural phenomena, 
though obscure, and while specifically de- 
nying any intention of considering them as 
fermentations, almost unconsciously ac- 
knowledged their affinity to fermentations 
by the name which he applied to them, and 
under which they have ever since been 
known, viz., the ‘zymotic’ or fermentative 
diseases. Dr. Farr gives no theory of their 
origin or causation and expressly declines 
to regard them as fermentations, partly, no 
doubt, because of the vehemence of Liebig, 
who was opposed to the idea, but also, we 
may believe, because the prevailing theory 
of the cause of fermentation was that it 
was due to the aggressive energy of free 
oxygen ; and it would have been obviously 
too absurd to assert that free oxygen, the 
very breath of human life, is at the same 
time the cause of its worst diseases. In 
Germany, Henle arrived, largely from obser- 
vation and @ priori reasoning, at a conclu- 
sion essentially similar to Dr. Farr’s, and, 
in America, Professor J. K. Mitchell, father 
of our distinguished physiologist and litter- 
ateur, Dr. Weir Mitchell, was urging, upon 
similar grounds, his able thesis ‘On the 
Cryptogamous Origin of Malarious and Epi- 
demic Fevers.’ 
