33(5 FERMENTATION ASCRIBED TO THE 



same water, was exposed for several weeks to the action of solar 

 light. During this time, a continued accumulation of gas took 

 place in the upper part of this jar ; after fourteen days £ of the 

 water in the jar had been pressed out of it, and the gas, which 

 had taken its place, ignited a glowing match of wood, and in 

 all respects behaved like pure oxygen gas. It must be here ex- 

 pressly stated, that the water, before being exposed to the action 

 of solar light, was examined by one of Ploessl's best micro- 

 scopes, without the detection of confervae or of any kind of ve- 

 getable matter.* 



Without venturing upon any opinion on the mode of nutrition 

 of these animals, it is quite certain that water containing living 

 infusoria becomes a source of oxygen gas when exposed to' the 

 action of light. It is also certain, that as soon as these animals 

 can be detected in the water, the latter ceases to act injuriously 

 to plants or animals ; for it is impossible to assume that pure 

 oxygen gas can be evolved from water containing any decaying 

 or putrefying matters, for these possess the property of combin- 

 ing with oxygen. Now it is obvious, if we add to such water 

 any animal or vegetable matter in a state of decay, that this, 

 being in contact with oxygen, will resolve itself into the ultimate 

 products of oxidation in a much shorter time than if infusoria 

 were not present. 



Thus we recognise in these animals, or perhaps only in certain 

 classes of them, by means of the oxygen which in some way, as 

 yet incomprehensible, accompanies their appearance, a most wise 

 and wonderful provision for removing from water the substances 

 hurtful to the higher classes of animals; and for substituting, in 

 their stead, the food of plants (carbonic acid), and the oxygen 

 gas essential to the respiration of animals. They cannot be 

 viewed as the causes of putrefaction, or of the generation of pro- 

 ducts injurious to animal and vegetable life ; but they make their 

 appearance in order to accelerate the conversion of putrefying 

 organic matter into its ultimate products. 



* One hundred cubic inches of water saturated with air contained, in 

 the form of air, according to the experiments of Humboldt and Gay-Lua- 

 mc, not above 1*6 cubic inches of oxygen gas. 



