Page:Popular Science Monthly Volume 10.djvu/674

654 upon here. It was almost impossible to save a cucumber; I never did succeed in saving a melon infusion from contamination, and from this so-called spontaneous generation. But here, when the air had been allowed to deposit all its motes, and when we were withdrawn from an infected atmosphere, as I have said, the chambers were returned with their infusions as clear as crystal. Mr. Cotterell will show you some of them. You will see that one of these is muddy and turbid, and it has a deposit at the bottom. These are all dead bacteria, and the muddiness is due to swarming bacterial life. Here you have two infusions perfectly clear. Why does the other tube give way? When we came to examine it, a little pinhole was found at the bottom of the chamber, and through that pinhole the germs got in. Here is a melon-infusion; and, in order to show you what would have occurred if the infusions had not been protected from the floating dust of the atmosphere, we have hung beside this case two tubes that have been exposed to the common air and have fallen into a state of utter rottenness. In this way, from the Jodrell Laboratory at Kew, we have had these cases returned with their infusions perfectly intact. Even in our infected atmosphere, when we subject our infusions to experimental conditions sufficiently stringent, we are able entirely to shut out contamination, and to show that spontaneous generation never occurs. When we get clear of our atmosphere altogether, this is a matter of perfect ease; and we find in Kew Gardens that Nature runs her normal course.



HE committee of the Albert Society has honored me by an invitation to give a few popular lectures at Dresden, on subjects of public hygiene. Let me state to you at once what I think of popular lectures in general.

What ought they to be, and what can we expect from them? I am not one of those who, in all their work and aim, look out directly for the practical use, for the return on the capital, immediate or prospective; but, on the other hand, I feel myself bound, in a certain degree, to inquire into the object of much that may appear to be either unprofitable or useless.

There is no doubt that popular lectures on scientific subjects will not impart really competent knowledge, and will not form experts.