LIMITS OF LIFE. 63 



ing science herself: will you yet rescue our 

 Biocosmos from extinction? 



Other limits of the Earth-life may be men- 

 tioned. It can hardly reach above seven miles 

 or so of the atmospheric envelope of the 

 giobe; on the other hand, it does not extend 

 very far below the terrestrial surface; thus 

 all living things exist on a thin globular shell. 

 There are also seasonal and zonal bounds 

 to vital activity upon the Earth's surface. 

 Scientists have brought to light a curious 

 fact about carbon dioxide (carbonic acid gas) 

 in the air. The animal expels it, the plant 

 takes it up ; too much of it in the atmosphere 

 destroys the animal, too little of it the plant. 

 Something similar may be said of other aerial 

 ingredients in reference to Life, for instance, 

 oxygen. The vital principle hovers on every 

 side between too-much and too-little ; all Life, 

 be it of the whole Earth or of one individual, 

 seems to hang fated between two mortal ex- 

 tremes. 



In some such fashion we have to draw the 

 limits of our Biocosmos. It is the one living 

 speck in the whole physical universe, as far 

 as man's knowledge goes, and we, each one 

 of us, are but a little brief speck of that 

 speck a microscopic microbe of the All. 

 Very limited in size and quantity, in place 

 and time is not only individual existence, but 



