88 APHORISMS AND REFLECTIONS 



eminent philosopher, but, I regret to have to add, 

 of his health. 



But the sacrifice has not been in vain. It is now 

 certain that this devastating, cholera-like P^brine 

 is the effect of the growth and multiplication of 

 the Panhistophyton in the silkworm. It is contagious 

 and infectious, because the corpuscles of the Pan- 

 hislophytt^n pass away from the bodies of the diseased 

 caterpillars, directly or indirectly, to the alimentary 

 canal of healthy silkworms in their neighbourhood ; 

 it is hereditary because the corpuscles enter into 

 the eggs while they are being formed, and con- 

 sequently are carried within them when they are 

 laid ; and for this reason, also, it presents the very 

 singular peculiarity of being inherited only on the 

 mother's side. There is not a single one of all the 

 apparently capricious and unaccountable phenomena 

 presented by the Pebrine, but has received its 

 explanation from the fact that the disease is the 

 result of the presence of the microscopic organism, 

 Panh istophyton. 



CCX.XII 



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 writh w^hat 

 smiles and shrugs, practical and serious contempo- 

 raries 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 themselves, could be of no conceivable utility to 

 mankind. 



