6GO FRAGMENTS OF 



possible a proportionate assent; and, if, it be a theory which 

 influences practice, our wisdom is to follow its probable 

 suggestions where more than probability is for the moment 

 unattainable. I write thus with the theory of contagiiim 

 vivum more especially in my mind, and must regret the 

 attitude of denial assumed by Professor Virchow toward 

 that theory. " I must beg my friend Klebs to pardon 

 me," he says, " if, notwithstanding the late advances 

 made by the doctrine of infectious fungi, I still persist in 

 rny reserve so far as to admit only the fungus which is 

 really proved, while I deny all other fungi so long as they 

 are not actually brought before me/ 7 Professor Virchow, 

 that is to say, will continue to deny the germ theory, 

 however great the probabilities on its side, however numer- 

 ous be the cases of which it renders a just account, until it 

 has ceased to be a theory at all, and has become a congeries 

 of sensible facts. Had he said, " As long as a single fungus 

 of disease remains to be discovered, it is your bounden 

 duty to search for it," I should cordially agree with him. 

 But by his unreserved denial he quenches the light of 

 probability which ought to guide the practice of the 

 medical man. Both here and in relation to the theory of 

 evolution excess upon one side has begotten excess upon 

 the other. 



CHAPTER XXXVIII. 



THE ELECTRIC LIGHT.* 



THE SUBJECT of this evening's discourse was proposed by 

 our late honorary secretary. f That word 'Mate" has for 

 me its own connotations. It implies, among other things, 

 the loss of a comrade by whose side I have worked for 

 thirteen years. On the other hand, regret is not without 

 its opposite in the feeling with which I have seen him rise by 

 sheer intrinsic merit, moral and intellectual, to the high- 

 est official position which it is in the power of English 

 science to bestow. Well, he, whose constant desire and 



* A discourse delivered at the Royal Institution of Great Britain on 

 Friday, January 17, 1879, and introduced here as the latest Frag- 

 ment. 



\ Mr. William Spottiswoode, late president of the Royal Society. 



