4i8 ELEMENTS OF BIOLOGY 



The Origin of Life. There is always an interest in the ques- 

 tion o£ the origin of Hfe. The problem is constantly being pro- 

 pounded to the biologist, for there are probably few rational minds 

 that do not at some time or other ask themselves this question. 

 But the present-day biologist, knowing that the facts are hidden 

 in a very remote past and that the answer is still in the very remote 

 future, is interested in the problem in only a mild way. A variety 

 of suggestions have been advanced, which may be conveniently di- 

 vided into several groups: 



(i) Special Creation: All living things were at some time cre- 

 ated from non-living materials by a supernatural power. Some 

 would limit special creation to the origin of Man only, holding 

 that other forms have arisen by the operation of natural laws. 



(2) Extra Terram: Life arrived on the earth by transfer from 

 interstellar space or from some other heavenly body. The suggestion 

 begs the question; it cannot be proved nor disproved and is wholly 

 speculative. 



(3) Spontaneous Generation: Life arose from non-living ma- 

 terials by the chance association of the various ingredients that now 

 compose living substance. A number of ingenious speculative 

 theories have been proposed, each supported by a variety of facts. 

 We will mention only the most commonly known facts here. In 

 the first place, protoplasm in order to be alive need contain but 

 twelve common elements which are found well distributed over 

 the earth. Secondly, water, also universally present, forms the 

 greatest proportion of protoplasm and many properties of proto- 

 plasm are also the properties of water. Thirdly, the salt content of 

 protoplasm is similar to that of sea water. Fourth, the energy- 

 releasing chemical reaction in protoplasm, oxidation, is also the 

 most common chemical reaction in the non-living world. Fifth, so 

 far as the problems have been investigated with success, protoplasm 

 obeys the laws and principles of Physics and Chemistry that apply 

 in the non-living world. According to the laws of probability, the 



