166 ANNIVERSAEY ADDEESS 



things — no one has ever seen, or smelt, or heard, or felt, or tasted 

 a germ ; neither have germs been weighed or analysed. But in my 

 opinion we may assume their existence from what may be called 

 circumstantial evidence. It is said that germs cause fermentation, 

 and that if you prevent the germs from getting to grapes or malt you 

 will not have fermentation. And again, if you prevent the access 

 of germs to a wound, or if you destroy them, you do not have 

 suppuration or offensive discharges. Thus originated what is called 

 antiseptic surgery, an invention only second to that of tbe sym- 

 pathetic powder, in which the applications were made, not to the 

 wound, but to the instrument that caused it. When our first 

 conversazione was held in this building, I exhibited twenty glasses, 

 each containing a different infusion. I placed in water twenty 

 different substances, as cheese, bread, sugar, honey, walnut shell, 

 etc. After a few days I examined the water with the micro- 

 scope. My object was to find out whether the animalculae varied 

 according to the kind of infusion. I found the same kind of 

 animal forms in each, although they varied in numbers and in 

 size in the different infusions. Those from the honey and the 

 sugar were the largest, those from hay most numerous, and the 

 walnut shell afforded the least in number and in size. I therefore 

 infer that the substances do not give rise to the animalculae, but 

 that the germs of them are floating in the air, and that the 

 infusions only afford a suitable habitation and food. 



A similar experiment is performed for us by Nature. In the 

 summer, a few days after rain, you will find the puddles by the 

 roadside become turbid. I noticed this very much last August, 

 a very wet month with us, and I was surprised at the different 

 colours presented by the puddles. Those on the roadside in Loates 

 Lane were green, some at Aldenham, brown, and some at Bricket 

 Wood, of a reddish colour. I cannot attribute this to difference of 

 soil. I thought it might be caused by different organisms in each. 

 I therefore examined them microscopically, but although all the 

 waters teemed with life, yet I could not determine the cause of 

 the various colours satisfactorily. I think there can be no doubt 

 that the germs of these organisms were floating in the air. The 

 subject forms part of the theory of Spontaneous Generation. The 

 conclusion that I have come to on this subject is this : that 

 spontaneous generation, speaking theoretically, is not only 

 possible but probable ; but that i)ractically it has not been proved. 

 Professor Tyndall says: "From the beginning to the end of 

 the inquiry, there is not, as you have seen, a shadow of evidence in 

 favour of the doctrine of spontaneous generation. There is, on the 



