in LIVING MATTER 67 



of oxygen and excretion of C0. 2 . W. Kochs (1892) used for this 

 purpose a large quantity of perfectly dry seeds of plants, which he 

 placed in large glass tubes from which the air had been pumped 

 out, and which were then hermetically sealed. After many 

 months, a minute analysis of the contents of the tubes failed to 

 detect any trace of carbonic acid; and yet the seeds perfectly 

 retained their capacity for germination. This experiment proves 

 that it is possible to establish a state of true potential life in the 

 seeds of certain plants. 



The results of a number of experiments undertaken by the 

 author in collaboration with Piutti (1888) on silk- worm eggs were 

 somewhat different. Without artificial desiccation these did not 

 entirely cease to breathe when kept for a long while at a 

 temperature of C., and even at that temperature they could not 

 survive prolonged exposure to an atmosphere of pure nitrogen. 

 When kept for 139 days in conical flasks in which the air was 

 maintained constantly dry by means of concentrated sulphuric 

 acid, they perished entirely if the temperature was 9-14 0., and 

 partly if it was C. It is therefore clear that under these 

 conditions the silk-worm eggs are reduced to a state of vita 

 minima. When placed in glass flasks, in which a perfect vacuum 

 was produced by the mercury pump, after which they were sealed 

 up and kept at C., more than half the eggs after 83 days were 

 alive, and capable of development when brought under normal 

 conditions of incubation. Here we have evidently a state of 

 minimal life approximating to that of latent life. Lastly, the 

 silk-worm eggs were placed under a glass bell-jar, hermetically 

 sealed to a plate and containing a desiccator with concentrated 

 sulphuric acid ; when after 128 days the enclosed eggs (which had 

 shrunk in an extraordinary way from the desiccation) hatched out, 

 a very copious but incomplete brood of caterpillars was produced, 

 which were smaller and less lively than the normal. From these 

 results it seems probable that insect eggs, like plant seeds, can be 

 artificially brought by desiccation into the state of latent or 

 potential life. According to Preyer's ingenious comparison, this state 

 is comparable to that of a clock wound up, but with the pendulum 

 arrested ; the state of death, on the contrary, is like a clock whicli 

 can no longer go because its wheels are broken. 



III. We saw in the last chapter that plants breathe like 

 animals, i.e. they take in oxygen, in order by a slow process of 

 combustion to form carbonic acid and water. The presence of 

 oxygen is, accordingly, one of the most fundamental conditions in 

 the active upkeep of metabolism. 



This does not mean that the presence of oxygen as such is 

 indispensable to the maintenance of life. In order to under- 

 stand its importance we must start with certain general con- 

 siderations. 



