DIGESTION. 207 



to positively decide whether these bodies when found in the tissues 

 are constituents of the living body or are only to be considered as 

 decomposition products formed after death. Leucin has been found 

 in the pancreas and its secretion, in the spleen, thymus and lymph- 

 glands, in the thyroid gland, in the salivary glands, in the kidneys, 

 brain, and liver (but mostly in disease). It also occurs in the wool 

 of sheep, in dirt from the skin (inactive epidermis) and between 

 the toes, and its decomposition products have the disagreeable odor 

 of the perspiration of the feet. It is found pathologically in 

 atheromatous ulcers, ichthyosis scales, pus, blood, and urine (in dis- 

 eases of the liver). Leucin also occurs in the vegetable kingdom. 



Leucin may be prepared synthetically most simply by the action 

 of ammonia on monobrom-caproic acid (HUFNER). On heating 

 with fuming hydriodic acid to 140 C. it splits into ammonia and 

 caproic acid. On heating leucin alone it decomposes with the for- 

 mation of carbon dioxide, ammonia, and amylamin. On fusing 

 with caustic alkali, as also on putrefaction, it yields valerianic acid 

 and ammonia. 



Leucin crystallizes when pure in shining, white, very thin 

 plates, usually forming round knobs or balls, either appearing like 

 hyalin or alternating light or dark concentric layers which consist 

 of radial groups of crystals. Leucin as obtained from the animal 

 fluids and tissues is very easily soluble in water and rather easily in 

 alcohol. Pure leucin is soluble with difficulty; it dissolves in 27 

 parts cold water, in 1040 parts cold and in 800 parts boiling alco- 

 hol. It is easily dissolved by alkalies and acids. On slowly heating 

 to 170 C. it melts and sublimes in white, woolly flakes which are 

 similar to sublimed zinc oxide. A marked odor of amylamin is 

 generated at the same time. 



The solution of leucin in water is not, as a rule, precipitated by 

 metallic salts. The boiling-hot solution may, however, be precipi- 

 tated by a boiling-hot solution of copper acetate. If the solution 

 of leucin is boiled with sugar of lead and then ammonia be added 

 to the cooled solution, shining crystalline leaves of leucin-lead oxide 

 separate. "When boiled with leucin, copper oxyhydrate is dissolved 

 without reduction. 



Leucin is recognized by the appearance of the balls or knobs 

 under the microscope, by its action when heated (sublimation test), 



