THE APPEARANCE OF LIFE 63 



hypothesis was self-destructive. In actual fact it solved no 

 problem at all. Wherever the germs of life may have come from, 

 it remains to explain how they originated in another world ; 

 the difficulty has merely been relegated to a farther sphere. 



All living organisms, moreover, consist of atoms of the same 

 nature. Carbon, hydrogen, nitrogen, and oxygen must at least 

 be present. These exist on the earth, as well as on other planets 

 that have passed, are still passing, or will pass through the same 

 stages of evolution. Why, it may be asked, should these 

 elements have united outside our earth and yet have remained 

 separate here ? This would indeed be contrary to the 

 fundamental principle of all science — that the same causes 

 always produce the same effects. If at any particular phase 

 in the evolution of the planets some sort of life has succeeded 

 in manifesting itself, the earth should be no exception to the 

 general rule. The task before us therefore is to investigate 

 fearlessly how, at some particular moment in the past, life 

 originated on this planet of ours, whereas now it can pass 

 only from one living organism to its successors. But, before 

 undertaking this task, we must first arrive at some agreement 

 as to what it is that constitutes living matter. 



It is not to be regarded as some special substance in which 

 life resides and which constitutes its unique and necessary 

 basis, something like an essentially unstable chemical com- 

 pound in a condition of perpetual change. On the contrary, it 

 consists of an assemblage of chemical compounds with sensitive 

 reactions which allow us, even during their living state, clearly 

 to differentiate and characterize them. Foremost among these 

 compounds are those which bear so much resemblance in their 

 constitution to the white of an egg that they have received the 

 name of albuminoid compounds. They consist of carbon, 

 hydrogen, nitrogen, oxygen, and a small quantity of some fifth 

 body : sulphur, phosphorus, or another substance. With these 

 so-called quaternary compounds are associated, in greater 

 or less quantities, ternary compounds consisting only of carbon, 

 hydrogen, and oxygen. Some of them contain more hydrogen 

 than is requisite for the formation of water in combination with 

 oxygen, while others can be considered as the result of a union 

 of carbon and water ; these latter are called carbo-hydrates. To 

 the first belongs the group of fats : sugars, dextrine, starch, 

 cellulose, etc., belong to the carbo-hydrates. None of these 



