1 00 Proceedings of the British Association. 



with fermentation. Yeast, according to my observations, when viewed 

 in a good achromatic microscope, consists altogether of translucent, 

 spherical and spheroidal particles, each of about the 6000th part of an 

 inch in diameter. When the beer in which they float is washed away 

 with a little water, they are seen to be colourless ; their yellowish tint, 

 when they are examined directly from the fermenting square or round 

 of a porter brewery, being due to the infusion of the brown malt. The 

 yeast of a square newly set seems to consist of particles smaller than 

 those of older yeast, but the difference of size is not considerable. The 

 researches of Shulze, Cagniard de la Tour, and Schwann, appear to show 

 that the vinous fermentation, and the putrefaction of animal matters — 

 processes which have been hitherto considered as belonging entirely to 

 the domain of chemical affinity — are essentially the results of an organic 

 development of living beings. This position seems to be estabhshed by 

 the following experiments : — 1 . A matrass or flask containing a few bits 

 of flesh being filled up to one-third of its capacity with water, was closed 

 with a cork, into which two slender glass tubes were cemented air-tight . 

 Both of these tubes were passed externally through a metallic bath, 

 kept constantly melted, at a temperature approaching to that of boiling 

 mercury. The end of one of the tubes, on emerging from the bath, 

 was placed in communication with a gasometer. The contents of the 

 matrass were now made to boil briskly, so that the air contained in it 

 and the glass tubes was expelled. The matrass being then allowed to 

 cool, a current of atmospherical air was made constantly to pass through 

 it from the gasometer, while the metallic bath was kept constantly hot 

 enough to decompose the living particles in the air. In these experi- 

 ments, which were many times repeated, no infusoria or fungi appeared, 

 no putrefaction took place, the flesh underwent no change, and the liquor 

 remained as clear as it was immediately after being boiled. As it was 

 found very troublesome to maintain the metallic bath at the melting pitch, 

 the following modification of the apparatus was adopted in the subse- 

 quent researches. A flask of three ounces capacity, being one-fourth 

 filled with water and flesh, was closed with a tight cork, secured in its 

 place by wire. Two glass tubes were passed through the cork ; the one 

 of them was bent down, and dipped at its end into a small capsule con- 

 taining quicksilver, covered with a layer of oil ; the other was bent on 

 leaving the cork, first into a horizontal direction, and downwards for an 

 inch and a half, afterwards into a pair of spiral turns, then upwards, 

 lastly horizontal, whence it was drawn out to a point. The pores of the 

 cork having been filled with caoutchouc varnish, the contents of the 

 flask were boiled till steam issued copiously through both of the glass 

 tubes, and the quicksilver and oil became as hot as boiling water. In 

 order that no living particles could be generated in the water condensed 

 beneath the oil, a few fragments of corrosive sublimate were laid upon 

 the quicksilver. During the boiling, the flame of a spirit lamp was 

 drawn, up over the spiral part of the second glass tube, by means of a 



