Permettez-moi de terminer ces quelques lignes que je dois dicter, vaincu que je suis par la maladie, en vous faisant observer que vous rendriez service aux Colonies de la Grande-Bretagne en répandant la connaissance de ce livre, et des principes que j'établis touchant la maladie des vers à soie. Beaucoup de ces colonies pourraient cultiver le mûrier avec succés, et, en jetant les yeux sur mon ouvrage, vous vous convaincrez aisement qu'il est facile aujourd'hui, nonseulement d'éloigner la maladie régnante, mais en outre de donner aux récoltes de la soie une prospérité qu'elles n'ont jamais eue. Origin and Propagation of Contagious Matter. Prior to Pasteur, the most diverse and contradictory opinions were entertained as to the contagious character of _pébrine_; some stoutly affirmed it, others as stoutly denied it. But on one point all were agreed. I They believed in the existence of a deleterious medium, rendered epidemic by some occult and mysterious influence, to which was attributed the cause of the disease.' Those acquainted with our medical literature will not fail to observe an instructive analogy here. We have on the one side accomplished writers ascribing epidemic diseases to 'deleterious media' which arise spontaneously in crowded hospitals and ill-smelling drains. According to them, the _contagia_ of epidemic disease are formed _de novo_ in a putrescent atmosphere. On the other side we have writers, clear, vigorous, with well-defined ideas and methods of research, contending that the matter which produces epidemic disease comes always from a parent stock. It behaves as germinal matter, and they do not hesitate to regard it as such. They no more believe in the spontaneous generation of such diseases, than they do in the spontaneous generation of mice. Pasteur, for example, found that _pébrine_ had been known for an indefinite time as a disease among silkworms. The development of it which he combated was merely the expansion of an already existing power--the bursting into open conflagration of a previously smouldering fire. There is nothing surprising in this. For though epidemic disease requires a special _contagium_ to produce it, surrounding conditions must have a potent influence on its development. Common seeds may be duly sown, but the conditions of temperature and moisture may be such as to restrict, or altogether prevent, the subsequent growth. Looked at, therefore, from the point of view of the germ theory, the exceptional energy which epidemic disease from time to time exhibits, is in harmony with the method of Nature. We sometimes hear diphtheria spoken of as if it were a new disease of the last twenty years; but Mr. Simon tells me that about three centuries ago tremendous epidemics of it began to rage in Spain (where it was named _Garrotillo_), and soon afterwards in Italy; and that since that time the disease has been well known to all successive generations of doctors. In or about 1758, for instance, Dr.