It is the fact that, from the year 1860 onward, numerous observers have experimented on the influence of very low temperatures upon seeds, and have uniformly shown that the power of germination and healthy growth of the seeds is not destroyed by exposure to very low temperatures. The celebrated Swiss botanist, De Candolle, published the first careful observations on this subject in conjunction with Raoul Pictet, who had devised an apparatus for producing exceedingly low temperatures. Pictet in 1893 exposed various bacteria and also seeds to a temperature of nearly 200 degrees below zero centigrade without injury to them. They "resumed" their life when gradually restored to the normal temperature. Pictet concluded that since all chemical action of the kind which goes on in living things requires a certain degree of temperature for its occurrence, and that this is demonstrably considerably higher than minus 100 degrees centigrade, we must suppose that all chemical action in living things (as in nearly all other bodies) is annihilated at 100 degrees below zero centigrade. Accordingly he maintained that what we call "life," or "living," is a manifestation of chemical forces similar to those shown in other natural bodies, and liable to interruption and resumption by the operation of unfavourable or favourable conditions as are other chemical processes. In 1897, Mr. Horace Brown and Mr. F. Escombe published, in the Proceedings of the Royal Society of London, an account of experiments in which they exposed seeds of twelve plants belonging to widely different natural orders to a temperature varying from 183 degrees to 192 degrees below zero centigrade for a period of 110 consecutive hours (about four days and a half). As a result the germinative powers of the seeds showed no appreciable difference from that of seed not subjected to cold, and they produced healthy plants. The low temperature was obtained by the use of liquid air in a vacuum-jacketed flask (like the well-known "thermos" flasks), into which the seeds were introduced in thin glass tubes. Professor M'Kendrick had previously shown that the putrescence of meat, blood and milk by bacteria infesting them was temporarily arrested, but not permanently so, by exposing those substances for one hour to a temperature of 182 degrees below zero centigrade. It appeared that the putrefactive bacteria present in those substances were not destroyed by that degree of cold, but returned to a state of activity when the normal temperature was restored. Professor M'Kendrick also showed that seeds would germinate after exposure to like treatment.