INTRODUCTION 



possibility of a spontaneous generation has been disproved by more 

 modern investigations ; the history of the development of intestinal 

 worms is known, and the germs of minute organisms have been 

 found to exist everywhere. SCHWANN and PASTEUR have been 

 pioneers in this work, and have shown that it is possible to hinder 

 the development of the lower organisms, in places where it is 

 customary to find them, by destroying all existing germs and at 

 the same time preventing the entrance of new ones. It is due to 

 the results obtained by these men in their investigations on 

 spontaneous generation that we are now able to preserve food in 

 a scientific manner. The germs previously existing in the substance 

 to be conserved are destroyed by heat, while, by a proper mode of 

 sealing, the entrance of new germs is rendered impossible, and the 

 decomposition, which their presence would occasion, is accordingly 

 prevented. 



All known living organisms have been derived from other 

 living organisms. But the idea of the origin of living from dead 

 substances has on the other hand derived important support from 

 the progress of chemical research. In the early decades of the 

 last century it was customary to draw a distinct line of separation 

 between organic and inorganic chemistry, and to assume that the 

 substances dealt with by organic chemistry could only be produced 

 by the vital action of organisms. The laws governing inorganic 

 chemistry appeared to have no reference to organic chemistry, the 

 formation of organic substance being due to a special force, the 

 li vital force." In 1828 WOHLER obtained urea from ammonium 

 cyanate, and thus for the first time produced an organic compound 

 from an inorganic substance. In 1845 KOLBE completely synthesised 

 trichloracetic acid, and in 1850 BERTHKLOT synthesised alcohol 

 and formic acid. The former substance had been synthetically 

 prepared by HENNEL in 1828, but BERTHELOT was the first to 

 recognise its identity with the substance formed in alcoholic 

 fermentation. By these results the former distinction between 

 organic and inorganic chemistry was destroyed. Organic chemistry 

 has become the chemistry of carbon compounds. 



In some such way it is possible that living matter originated from 

 non-living at some period in the evolution of the earth when the 

 conditions for its formation existed. In order that the organic 

 world should have developed from the first living matter, one of 

 the original properties of the latter must have been a capability of 

 continued existence among its surroundings. It must have been 

 capable of variation and of retaining the new characters appearing 

 in this way, of growth, i.e. the increase of itself at the cost of 

 foreign substances, and of reproduction, i.e. multiplication by 

 separation into a number of parts. Some observers have recently 

 described the origin of microscopic structures which behave similarly 



