2G2 ANNUAL OF SCIENTIFIC DISCOVERY. 



ease, in being hereditary, and in being, under some circum- 

 stances, contagious, as well as infectious. The Italian naturalist, 

 Filippi, discovered in the blood of the silkworms affected by this 

 strange disease, a multitude of cylindrical corpuscles, each about 

 one six-thousandth of an inch long. These have been carefully stud- 

 ied by Lebert, and named by him Panliistopliyton ; for the reason 

 that, in subjects in which the disease is strongly developed, the cor- 

 puscles swarm in every tissue and organ of the body, and even pass 

 into the undeveloped eggs of the female moth. But are these cor- 

 puscles causes, or mere concomitants, of the disease ? Some natural- 

 ists took one view and some another ; and it was not until the French 

 government, alarmed by the continued ravages of the malady, and 

 the inefficiency of the remedies which had been suggested, dis- 

 patched M. Pasteur to study it, that the question received its final set- 

 tlement, at a great sacrifice, not only of the time and peace of mind 

 of that 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 Pebrine is the effect of the 

 growth and multiplication of the Panliistopliyton in the silkworm. It 

 is contagious and infectious, because the corpuscles of the Panliis- 

 topliyton pass away from the bodies of the diseased caterpillars, 

 directly or indirectly, to the alimentary canal of healthy silk- 

 worms in their neighborhood ; it is hereditary, because the cor- 

 puscles enter into the eggs while they are being formed, and 

 consequently 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 Panliistopliyton. 



" Such being the facts with respect to the 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 gener- 

 ated. If it may be generated by abiogenesis, or by xenogenesis, 

 within the silkworm or its moth, the extirpation of the disease 

 must depend upon the prevention of the occurrence of the con- 

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

 other hand, the Panliistopliyton is an independent organism, which 

 is no more generated by the silkworm than the mistletoe is gener- 

 ated 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 "Panliistopliyton. As might be imagined, from the 

 course of his previous investigations, M. Pasteur was led to be- 

 lieve that the latter was the right theory ; and guided by that the- 

 ory, 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, contagious and infectious diseases, of great malig- 

 nity, are caused by minute organisms which are produced from 



