LIFE 27 



microscope revealed the minute forms of plant and animal life which 

 exist and which were immediately conceived by many to be spontaneously 

 generated when the right conditions occur. The work of Pasteur in 

 France and Tyndall in England during the latter part of the last century, 

 however, disproved the possibility of spontaneous generation of even these 

 minute forms. There are those today who entertain a belief in the 

 possibility of the spontaneous generation of life, but there is no existing 

 evidence to support their views. 



Another theory of the origin of life held by the physicists, Kelvin 

 and Helmholtz, who also lived in the last century, explains the presence 

 of life on the earth by stating that it was brought here on meteorites 

 through the interstellar spaces from some other world. This meteoritic 

 theory is frequently coupled with the conception that life has always 

 existed in this universe and is simply passed from one world to another 

 from time to time. This is unsatisfactory to biologists, because it puts 

 the whole problem beyond the possibility of human explanation, and 

 because the conditions which would have to be withstood by life coming 

 to this planet in that way are apparently beyond the limits of endurance 

 of living matter. For this reason the theory has been believed in by 

 only a few, and these not biologists. 



Another theory of the origin of life, formulated by a German, Pfiiiger, 

 in the latter part of the last century, has been known as the cyanogen 

 theory. According to this theory the earth was once exceedingly hot and 

 the elements were in a free state. As it cooled a temperature and other 

 conditions were reached which caused the union of carbon and nitrogen 

 into a substance known as cyanogen, the formula for which is CN. As 

 the earth cooled still more, water was formed by the union of hydrogen 

 and oxygen; and then by the combination of cyanogen and water, cyanic 

 acid (HCNO) was produced. The characteristics of cyanic acid resemble 

 in many ways those of protoplasm: (1) It is a liquid which is transparent 

 at low temperatures, but it tends to coagulate and become opaque at high 

 temperatures. (2) It can increase in bulk by a process essentially hke 

 that of growth by intussusception. (3) Its molecules can be rearranged to 

 form urea and it can be decomposed into carbon dioxide and ammonia. 

 By the addition of sulphur and other elements to cyanic acid, proteins 

 might have been formed and thus life might have developed. 



Another, known as the bacterial theory, is that of Osborn, who places 

 the origin of life at a time when there was no soil on the surface of the 

 earth, when all the water was fresh, and the air contained more carbon 

 dioxide than at present. At that time the earth was shrouded in a dense 

 cloud through which the sun never penetrated. This cloud was main- 

 tained by constant evaporation from the heated surface of the earth. 

 The air was warm and saturated with moisture. Lightning played 

 constantly through the clouds and rain descended in torrents. Under 



