CHAPTER XIV 



IDENTIFICATION OF GROWTH-SUBSTANCES 

 AND SUBSTANCES RELATED TO THEM 



Animal substances are much more compound than those 

 we have hitherto examined. Several of the substances 

 furnished by animals still preserve many of the properties 

 of the vegetables by which they are nourished. — Beaum6. 



The following selected information is given in the hope that it 

 will be useful to those proposing to undertake the search for 

 growth-substances in agricultural materials such as manure 

 and compost. As no work has yet been done along such lines 

 (except for the early isolations from decomposed meat) the 

 available information will require to be specially adapted to 

 suit each worker's need. The existing qualitative tests refer 

 entirely to the identification of the pure substances in aqueous 

 solution or as they occur in urine. When urine is mentioned 

 here, it is usually human urine that is implied. 



Critical methods of identifying the growth-substances are 

 urgently required. No progress can be made in the recogni- 

 tion and estimation of the substances in organic manures and 

 decomposition products until simple yet accurate chemical 

 tests are available. Much of the information that is available 

 is published in medical and physiological journals difficultly 

 accessible to agricultural and other chemists. The handbooks 

 on organic chemistry give very little help of the kind useful 

 for performing analysis of extracts, and it seems that the 

 detection of ring-compounds in manure and composts will 

 remain for some time a matter for the research laboratory 

 able to isolate the substances for characterization by such 

 criteria as melting points. (See Tabular Index, Chapter XV). 

 Such methods are not only laborious, but are seldom suscep- 



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