SPONTANEOUS CONGESTTON AND INFECTIOUS DISEASES. 763 
organism, panhistophyton. Such being the facts with respect to Pebrine, 
what are the indications as to the method of preventing it ? It is obvious 
that this depends upon the way in which the panhistophyton is generated. 
If it may be generated by abiogenesis, or by xenogenesis, within the silk- 
worm or its moth, the extirpation of the disease must depend upon the pre- 
vention of the occurrence of the conditions under which this generation takes 
place. But if, on the other hand, the panhistophyton is an independent or- 
ganism, which is no more generated by the silkworm than the mistletoe is 
generated by the oak, or the apple tree, on which it grows, though it may 
need the silkworm for its development in the same way as the mistletoe 
needs the tree, then the indications are totally different. The sole thing 
to be done is to get rid of and keep away the germs of the panhistopyhton. As 
might be imagined, from the course of his previous investigations, M. 
Pasteur was led to believe that the latter was the right theory ; and guided 
by that theory, he lias devised a method of extirpating the disease, which 
has proved to be completely successful wherever it has been properly carried 
out. There can be no reason, then, for doubting that, among insects, con- 
tagious and infectious diseases, of great malignity, are caused by minute 
organisms which are produced from pre-existing germs, or by homogenesis ; 
and there is no reason, that I know of, for believing that what happens in 
insects may not take place in the highest animals. Indeed, there is already 
strong evidence that some diseases of an extremely malignant and fatal 
character to which man is subject, are as much the work of minute organ- 
isms as is the Pebrine. I refer for this evidence to the very striking facts 
adduced by Professor Lister in his various well-known publications on the 
antiseptic method of treatment. It seems to me impossible to rise from the 
perusal of these publications without a strong conviction that the lamen- 
table mortality which so frequently dogs the footsteps of the most skilful 
operator, and those deadly consequences of wounds and injuries which seem 
to haunt the very walls of great hospitals, and are, even now, destroying more 
men than die of bullet or bayonet, are due to the importation of minute 
organisms into wounds, and their increase and multiplication ; and that the 
surgeon who saves most lives will be he who best works out the practical 
consequences of the hypothesis of redi. 
I commenced this address by asking you to follow me in an attempt to 
trace the path which has been followed by a scientific idea, in its long and 
slow progress from the position of a probable hypothesis to that of an 
established law of nature. Our survey has not taken us into very attractive 
regions ; it has lain chiefly in a land flowing with the abominable, and 
peopled with mere grubs and mouldiness. And it may be imagined with 
what smiles and shrugs practical and serious contemporaries of Redi and of 
Spallanzani may have commented on the waste of their high abilities in 
toiling at the solution of problems which, though curious enough in them- 
selves, could be of no conceivable utility to mankind. Nevertheless, you 
will have observed, that before we had travelled very far upon our road 
there appeared, on the right and on the left, fields laden with a harvest of 
golden grain, immediately convertible into those things which the most 
sordidly practical of men will admit to have value — namely, money and life. 
The direct loss to Trance caused by the Pebrine in seventeen years cannot 
be estimated at less than fifty millions sterling ; and if we add to this what 
Redi’s idea, in Pasteur’s hands, has done for the wine-grower and for the 
vinegar-maker, and try to capitalise its value, we shall find that it will go a 
long way towards repairing the money losses caused by the frightful and 
calamitous war of this autumn. And as to the equivalent of Redi’s thought 
in life, how can we overestimate the value of that knowledge of the nature 
of epidemic and epizootic diseases, and consequently of the means of 
