218 THE CONSTITUENTS OF PLANTS. IX. 



5. Allantoine, C 4 H 6 N 4 3 , found principally in animal pro- 

 ducts, has been detected in certain vegetables, e.g., in plane- 

 tree leaves and in the sprouts of many young plants and in 

 cereals. It crystallizes in prisms, soluble in hot water and in 

 alcohol, and has a neutral reaction. It is di-ureide of glyoxylic 

 acid and has the constitution 



NH CH NH 



CO 



CO NH, 



NH CO 



6. Lez^we, ::: amido-caproicacid,CH 3 .(CH 2 ) 8 .CH(NH 2 ).COOH, 

 occurs in many animal substances, e.g., the liver, spleen, 

 pancreas, &c., and in many vegetable products, e.g., vetch 

 sprouts, the pumpkin, &c. It is also formed readily from 

 many albuminoids by the action of sulphuric acid, ferments, 

 or caustic potash. It is a white crystalline substance, melting 

 at 170 and volatile without decomposition. Its solubility in 

 water is not great and it is less soluble in alcohol. It dissolves 

 readily in either acid or alkaline solutions. 



7. Tyro sine, paraoxyphenyl-a-amido-propionic acid, C, ; H 4 

 (OH).CH 2 .CH(NH.,).COOH., often accompanies leucine as a 

 product of the action of digestive enzymes upon albuminoids. 

 It crystallizes in fine needles and is readily soluble in hot 

 though only sparingly in cold water ; it is insoluble in ether 

 or alcohol. 



The amides play an important part in plant nutrition. 

 Being soluble and diffusible they can readily pass from one 

 part of the plant to another, which is not the case with the 

 colloidal albuminoids. 



The amides are apparently not capable of forming flesh in 

 an animal, though they doubtless aid in fat formation and in 

 heat evolution. It is evidently very important, therefore, to 

 discriminate between amides and albuminoids in examining 

 vegetable food stuffs. In many analyses which have been 

 published this has not been done, and in the case of certain 

 varieties of foods, e.g., roots, the results obtained in practice 

 do not correspond with what might be expected from the 



* According to Fischer (Ber. 33, 2371), leucine is a-araido-isobutyl acetic acid, 

 (CH 3 > 2 . CH. CH 2 . CH(XH. 2 ). COOH. 



