570 FRAGMENTS OF SCIENCE. 
ricidal media are therefore antiseptic and disinfecting."* 
It was these organisms acting in wound and abscess which 
so frequently converted our hospitals into charnel-houses, 
and it is their destruction by the antiseptic system that 
now renders justifiable operations which no surgeon would 
have attempted a few years ago. The gain is immense 
to the practicing surgeon as well as to the patient practiced 
upon. Contrast the anxiety of never feeling sure whether 
the most brilliant operation might not be rendered 
nugatory by the access of a few particles of unseen hospital 
dust, with the comfort derived from knowledge that all 
power of mischief on the part of such dust has been surely 
and certainly annihilated. But the action of living con- 
tagia extends beyond the domain of the surgeon. The 
power of reproduction and indefinite self-multiplication 
which is characteristic of living things, coupled with the 
undeviating fact of contagia "breeding true,'' has given 
strength and consistency to a belief long entertained by 
penetrating minds, that epidemic diseases generally are 
the concomitants of parasitic life. " There begins to be 
faintly visible to us a vast and destructive laboratory of 
nature wherein the diseases which are most fatal to animal 
life, and the changes to which dead organic matter is 
passively liable, appear bound together by what must at 
least be called a very close analogy of causatipu." f Accord- 
ing to this view, which, as I have said, is daily gaining 
converts, a contagious disease may be defined as a conflict 
between the person smitten by it and a specific organism 
which multiplies at his expense, appropriating his air and 
moisture, disintegrating his tissues, or poisoning him by 
the decompositions incident to its growth. 
During the ten years extending from 1859 to 
researches on radiant heat in its relations to the gaseous 
form of matter occupied my continual attention. When 
air was experimented on, I had to cleanse it effectually of 
* In his last excellent memoir Colin expresses himself thus: " Wer 
noch heut die Faulniss von einer spontanen Dissociation der Pro- 
teinmolecule, oder von einem unorganisirten Ferment ableitet, oder 
gar aus ' Stickstoffsplittern ' die Balken zur Stiitze seiner Faul- 
nisstheorie zu zinnnern versucht, hat zuerst den Satz 'keine 
Faulniss ohne Bacterium Termo ' zu widerlegen." 
\ Report of the Medical Officer of the Privy Council, 1874, p, 5, 
