50 THE VITAMINES 



in the first stages of metabolism; perhaps they are responsible for 

 the sudden onset of cell division. In organisms which multiply by 

 conjugation or copulation, the vitamines or similar substances exert 

 some influence perhaps in the subsequent nucleus and protoplasm 

 partition. When we compare the quiescent with the sprouting seed, 

 we see the difference between the living and the dead tissue, although 

 the gross chemical compositions in both conditions are not far 

 different from each other. The entire difference may be due to the 

 formation of an active vitamine modification. It is evident that no 

 great progress is made when an unknown matter is explained by 

 something equally unknown. It may nevertheless be of value, as 

 far as future investigations are concerned, to point out in which 

 class of chemical bodies the substances essential to life are to be 

 sought. 



Clark (110) described the influence and characteristics of a sub- 

 stance which he called "Oocytin," and which was supposed to be 

 able to bring about the formation of the fertilization membrane of 

 sea urchin eggs, previously treated with strontium chloride. This 

 substance was prepared in powdered form from centrifuged and 

 defibrinated ox blood. The powder gave the reaction of protein, 

 purine, and pentose, and contained only a small amount of phos- 

 phorus. It was inactivated by heating to 73 to 80C., or by long 

 contact with alcohol. Similar substances were demonstrated in the 

 sperm of the sea urchin by Robertson (111). These or other active 

 substances naturally play a similar part in the plant kingdom, 

 although they are for the moment unavailable for physiological- 

 chemical work. 



The question as to the ability of certain types of plants and par- 

 ticular parts of plants to build up vitamines is still far from solution. 

 In higher plants, for example, there are three possibilities: 



1. In seeds, stored up vitamines suffice to stimulate further 

 synthesis of vitamines in the growing parts of the plants. 



2. It is possible that the small amount of vitamines in seeds suffices 

 to carry the plants along to a certain stage, from which there is a 

 symbiosis with certain microorganisms which provide the plants with 

 vitamines. 



3. It is possible that some of the plant structures, for example, 

 the leaves, possess the ability to synthesize certain vitamines. 



