104: CRYSTALLIZABLE NITROGENOUS MATTERS. 



little more than 0.5 per cent. It is, therefore, undoubtedly a constitu- 

 ent of the medullary layer of nerve fibres. 



Leucine, C 6 H 13 N0. 2 , 



So called from the glistening white color of its crystals. It is found 

 in the tissue of the spleen, the thymus, thyroid, lymphatic, submaxillary, 

 and parotid glands, the pancreas and pancreatic juice, the brain, liver, 

 kidneys, and supra-renal capsules. In all these situations it exists in 

 comparatively small quantity, but its exact proportions have not been 

 determined. ' It has not yet been found in the blood in a state of health, 

 and has only been met with in the urine in certain cases of disease. 

 According to Hoppe-Seyler it is one of the products of putrefactive 

 decomposition of albuminous and gelatinous substances. When pure, 

 it crystallizes in thin white laminae, in which form it is readily solu- 

 ble in water, less so in alcohol, and insoluble in ether. Heated 

 slowly to 170 (338 F.) it volatilizes unchanged; above this point it 

 is decomposed ; two of the products of its decomposition being carbonic 

 acid and ammonia. But little is known with regard to the normal 

 origin or physiological destination of this substance, its importance 

 being only indicated by the number and variety of the situations in 

 which it is found. 



Sodium Glycocholate, C 26 H 42 N0 6 Na. 



This is one of the characteristic ingredients of the bile, where it 

 sometimes forms, according to the observations of Jacobsen, nearly 49 

 per cent, of the dry residue. It is also found in the tissue of the liver 

 and in the fluids of the upper part of the intestinal canal, into which 

 it is discharged with the bile ; but it does not exist in the blood or in 

 the other animal fluids. 



It is a saHne body, consisting of a nitrogenous organic acid, glyco- 

 cholic acid (C 26 H 43 N0 6 ) in combination with sodium. Glycocholic acid 

 is so called because by boiling with solutions of potassium hydrate or 

 baryta water, or by continued boiling with dilute hydrochloric or 

 sulphuric acids, it is decomposed with the production of two new 

 bodies, namely, glycine (C 2 H 6 N0 2 ), a nitrogenous neutral substance, 

 and cholic acid (C 24 H 40 5 ), a non-nitrogenous organic acid, so called 

 because peculiar to the bile. This change takes place with the assump- 

 tion, by the glycocholic acid, of the elements of water, as follows : 



Glycocholic acid. Glycine. Cholic acid. 



C 26 H 43 N0 6 + H 2 = C 2 H 5 N0 2 + C 24 H 40 5 . 



The two bodies thus formed do not, therefore, pre-exist in the organic 

 acid of the bile, but are produced, by the addition of other elements, 

 at the time of its decomposition. 



Sodium glycocholate is a neutral, crystallizable substance, very 

 soluble in water and in alcohol, and insoluble in ether. It is accord- 

 ingly extracted from the bile by the following process : The bile is first 

 evaporated to dry ness over the water-bath, the dry residue extracted 



