THE VITAMINES IN THE ANIMAL KINGDOM 81 



animals investigated at various biological experimental stations, 

 where observations which would be of interest to us have undoubtedly 

 been made on the modes of nutrition of many insects. Unfortunately, 

 these data were unavailable to us. 



METAZOA 



Coming to the polycellular animals, we shall first describe a series 

 of experiments undertaken for some other purposes. They deal with 

 the influence of lecithin upon growth and were carried out by Goldfarb 

 (223). In this respect, he investigated a whole series of animals, and 

 also tadpoles and eggs of the starfish. At first, he stated emphati- 

 cally that lecithin had a definite action, but in a later work (224), 

 he admitted that it was inactive. This is apparently associated 

 with a vitamine impurity, whose presence may vary with the mode 

 of preparation of lecithin. 



It may not be amiss to say a few words here on Carrel's tissue 

 culture in vitro, which in the future may perhaps be of help in advanc- 

 ing the vitamine problem. These tissue cultures may be thought of 

 as polycellular organisms. 



The growth of tissue in vitro 



Most of the experiments of Carrel were made at a time when the 

 vitamines were either unknown or given very little consideration; 

 otherwise it might have been possible to choose still better conditions 

 for tissue culture. We must admit, however, that Carrel practically 

 foresaw the future trend of work, in that he chose the natural juices . 

 of the animal organism as the nutritive solutions. Inasmuch as the 

 author has little practical knowledge of this method, he is naturally 

 not in a position to judge whether or not Carrel would have obtained 

 even better results if he had tested his nutritive solutions for the 

 presence of all the necessary elements for nutrition. Because of the 

 great interest that experimental surgery of the future may have in 

 this method, it is very important to obtain the greatest success. 

 The tissue fragments used in these experiments, are removed from 

 their normal environment and must then lead an independent exist- 

 ence. For this purpose, they need all of the dietary constituents 

 (also vitamines) designated as essential by the modern science of 



