Ixxxviii REPOKT — 1870. 



side. There is not a single one of all the apparently capricious and un- 

 accountable phenomena presented by the Pebrino, but has received its expla- 

 nation from the fact that the disease is the result of the presence of the mi- 

 croscopic organism Panhistophyton. 



Such being the facts with respect to the Pobrlue, what are the indications 

 as to the method of preventing it ? It is obvious that this depends upon the 

 way in which the Fanhistopliyton is generated. If it may be generated by 

 Abiogenesis, or by Xenogenesis, within the silkworm or its moth, the extirpa- 

 tion of the disease must depend upon the prevention of the occurrence of the 

 conditions under which this generation takes place. But if, on the other 

 hand, the Panhistophyton is an independent organism, 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 de- 

 velopment in the same way as the mistletoe needs the tree, then the indica- 

 tions are totally different. The solo thing to be done is to get rid of and 

 keep away the germs of the Panhistophyton. As might be imagined, from 

 the course of his previous investigations, il. Pasteur was led to believe that 

 the latter was the right theory ; and guided by that theory, he has 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, conta- 

 gious and infectious diseases, of great malignity, are caused by minute orga- 

 nisms which are produced from preexisting germs, or by Homogeuesis ; 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 organisms as is 

 the Pebrino. 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 

 those publications without a strong conviction that the lamentable mortality 

 which so frequently dogs the footsteps of the most skilful operator, and 

 those deadly consequences of wounds and injuries which seem to haunt tho 

 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 esta- 

 blished 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 mouldincss. And it may be imagined with 

 what smiles and shrugs practical and serious contemporaries of Redi aad 

 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 hand and on the left, fields laden 

 with a harvest of golden grain, immediately convertible into those things 



