i 88 SCIENCE FROM AN EASY CHAIR 



perature above that of boiling water the gases, when 

 they unite, contract to form water-vapour, three pints of 

 the uniting gases (consisting of two pints of hydrogen 

 and one of oxygen) forming two pints only of water- 

 vapour. This, when it is cooled to a temperature below 

 212 deg. Fahr., suddenly contracts to a few thimblefuls 

 of pure liquid water. Neither oxygen nor hydrogen 

 "uncombined" liquefy till far below zero. 



A proteid, in the same way, is a chemical combina- 

 tion of the elements already mentioned carbon, oxygen, 

 hydrogen, nitrogen, and sulphur but the proportions by 

 volume of these elements to each other are represented 

 by very high figures, not merely by two to one, as in the 

 case of water. It is the carbon in them that makes " pro- 

 teids " turn black when they are destroyed by burning, 

 and it is the sulphur which causes the smell of rotten 

 eggs. Whilst an ultimate molecule or physical particle 

 of water consists of two atoms of hydrogen and one of 

 oxygen the molecule of the proteid called " albumen " 

 is built up by seventy-two atoms of carbon, one hundred 

 and twelve atoms of hyrodgen, eighteen atoms of nitrogen, 

 twelve atoms of oxygen, all brought into relation with 

 one atom of sulphur. Probably in some other proteids 

 the number of these atoms must all be multiplied by 

 .three. The elaborate " atomic composition " of a 

 molecule of proteid renders it very unstable ; it easily 

 falls to pieces, the elements combining, in other and 

 simpler proportions, to form less "delicate" bodies. Living 

 protoplasm consists chiefly of proteids and of compounds 

 which are on the way up, forming step by step more 

 elaborate combinations till they reach the proteid stage 

 and of many others which are degradation products, 

 coming down, as it were, from the giddy heights of the 

 proteid combination. The protoplasm of a cell contains 

 finer and grosser granules, which are these ascending 



