OCCURRENCE AND FORMATION OF GROWTH SUBSTANCES 67 



Hence, formation of the hormone probably would not be influ- 

 enced by irradiation of the coleoptile alone. 



Production of Auxin in Human Urine. — Kogl, Haagen Smit, 

 and Erxleben (1933, Mitt. IV) prepared a crystallized growth 

 substance from human urine. It was obtained from the bicar- 

 bonate fraction in the preparation of the follicle hormone from 

 the urine of a pregnant woman. Later it was prepared from 

 mixed urine from the Utrecht clinics. The total growth- 

 substance content of normal urine is about 80 per cent auxentriolic 

 acid (auxin a) and 20 per cent 3-indole acetic acid (heteroauxin) 

 according to later investigations by these same workers (Kogl, 

 Haagen Smit, and Erxleben, 1934, Mitt. XI and XII). 



Human urine ordinarily contains from 1 to 2 mg. of growth 

 substance per liter, irrespective of age, sex, or such pathological 

 conditions as carcinoma and tuberculosis (Kogl, Haagen Smit, 

 and Erxleben, 1933, Mitt. VII). Auxin elimination was some- 

 what higher than normal in cases of diabetes, probably owing to 

 an abundance of fats. In the average individual the auxin 

 excretion comprises about 20 per cent of the quantity ingested. 

 The excretion in the first few hours after a meal has the highest 

 content of auxin (Fig. 20 A). Diets high in fats are more effective 

 than others in producing an "auxin peak" after meals (Fig. 205) ; 

 the ingestion of hydrogenated fats is without effect. If arachis 

 (peanut) oil is subjected to the action of hpase, its products 

 possess growth-promoting properties ; tliis may explain why diets 

 high in fats lead to high auxin production in the urine. 



The source of growth substance in the saliva and urine of the 

 human body still remains to be explained satisfactorily (Kogl, 

 Haagen Smit, and Erxleben, 1933, Mitt. VII). A portion of the 

 growth substance in saliva doubtless is produced by bacteria in 

 the mouth. That it is produced probably by bacteria in the 

 intestines is indicated by the fact that human feces carry a 

 significant amount of growth substance (Kogl and Haagen Smit, 

 1931, Mitt. I); this is probably largely absorbed by the body. 

 According to Kogl and his coworkers, the growth substance 

 produced by intestinal bacteria constitutes only a small portion 

 of the auxin in urine. Significant amounts of growth substance 

 are consumed in food. The hourly elimination of auxin in urine 

 shows a maximum at eight o'clock in the evening following the 

 main meal at six o'clock. The ingestion of grape sugar, starch, 



