LIFE, CARBON'S OUTSTANDING PROPERTY 67 



enzymes artificially; that task is too difficult for present- 

 day chemistry. Another difficulty arises from the fact 

 that the chemical changes in tissues depend in many in- 

 stances on the simultaneous presence of several enzymes. 

 In such a case we may consider ourselves successful if 

 we know one of these jointly-operating ferments. In this 

 class belong the well known vitamins, small amounts of 

 which are hidden in the grosser foods. After being taken 

 up with the food they are rapidly used up in the body, and 

 consequently must be refed continually to keep the body 

 economy working. Failing this, the entire body mechanism 

 is deranged and grave disease follows; it often occurred 

 before vitamins were known, for instance the scurvy of 

 sailors from the lack of fresh fruit and vegetables, containing 

 vitamin C. 



Another type of "partial" ferments are the hormones. 

 They are made inside the body by the glands of internal 

 secretion and transported by the blood to that part of the 

 body where they have their greatest activating influence. 

 A well known hormone is insulin, the administration of 

 which is the chief treatment for diabetes. 



5. THE PROBLEM OF SPONTANEOUS GENERATION OF LIFE 



We hope that the knowledge of some of the essential 

 features of life processes will help us to form at least some 

 conception of the origin of life on our earth. Any explana- 

 tion must, of necessity, be very uncertain in the present 

 state of our knowledge, but we may hope that some clues 

 may be found. 



Whence did life on our earth come? How did it origi- 

 nate? Strenuous attempts have been made to answer this 

 question. Up to the middle of the last century the idea of 

 spontaneous generation was prevalent. If plants were 

 suddenly found to grow upon a previously barren soil, it 



