CHAP. IX.] THE INTESTINAL JUICE OR ' SUCCUS ENTERICUS.' 405 



even though it has been previously boiled with concentrated nitric 

 acid. Were the phosphorus of reticulin dependent on admixture 

 with nuclein, dilute nitric acid Would extract from it metaphosphoric 

 acid, and after boiling with nitric acid the reactions of tribasic 

 phosphoric acid would be obtained. 



When heated with diluted solutions of the caustic alkalies 

 reticulin yields a phosphorus-free proteid body and a phosphorus- 

 containing organic compound, which is soluble in chloroform and 

 alcohol, but insoluble in ether or water ; it is therefore clear that the 

 phosphorus of reticulin is not due to a nuclein residue. 



Products of As already stated (note 5, p. 244) reticulin when 

 ie decomposi- su bj ecte( } to long boiling with stannous chloride and 

 tion of reti- , f , , . ? i i " * r-j 



culin when de- hydrochloric acid yields as chief products of decom- 



composed with position, amido-valerianic acid, besides sulphuretted 

 hydrochloric hydrogen, ammonia, lysine and lysatinine, but neither 

 leucine nor tyrosine. 



SECT. 3. THE INTESTINAL JUICE OR Succus ENTERICUS. 



By the name of intestinal juice, or succus entericus, we designate 

 the liquid which is secreted by the glands found in the mucous 

 membrane of the small intestine. Although we are now in posses- 

 sion of ingenious methods which enable us to make valuable observa- 

 tions on the processes of intestinal digestion, the difficulties of obtain- 

 ing sufficient quantities of intestinal juice, under perfectly normal 

 conditions, are so great as to lead us to attach very little value to the 

 published quantitative analyses of the secretion. Moreover, it seems 

 likely that the intestinal juice is not absolutely identical in all 

 sections of the intestinal tract. 



In the duodenum, for instance, the secretion of the glands of 

 Lieberkiilm is mixed with that of the glands of Briinner, the function 

 of which is but imperfectly understood. In some animals, these 

 glands appear to have the structure and the functions of the pyloric 

 glands of the stomach ; in others they probably are rather analogous 

 to the pancreas. But leaving the duodenum out of the question, we 

 are already in possession of facts which indicate that the amount of 

 secretion and its chemical activities are by no means identical in the 

 upper and the lower reaches (if we may use the expression) of the 

 intestinal canal. These facts will be referred to in the sequel. 



The Methods of obtaining Intestinal Juice. 



The earlier workers either made observations on the contents of 

 the small intestines of animals which had for a long time been 



