CHEMICAL BASIS OF THE ANIMAL BODY. 95 



of the dextrin s to complete conversion into sugar 1 . Although this 

 statement is based upon experiments made with saliva, there is no 

 reason to suppose that the same will not hold good in the case of the 

 pancreatic juice by whose action the chief carbohydrate digestion of 

 the body is carried on. We shall therefore not be far wrong in 

 concluding that in the animal body starch is completely converted into 

 sugar previous to absorption, and if this be the case the interest of the 

 physiologist in the primary products of starch hydrolysis becomes very 

 small, except so far as a study of these products is essential to the 

 elucidation of the probable molecular magnitude and structure of the 

 parent-substance. 



When starch is treated with dilute boiling acids, the products 

 which have been so far described are formed in rapid succession, the 

 whole being finally converted into dextrose 2 . 



4. Animal-gum (C 12 H 20 O 10 + 2H 2 0) (?). 



This is according to Landwehr a form of carbohydrate which may 

 be extracted by the prolonged action of superheated water from 

 salivary and mucous glands, and is found also in milk and urine. 

 It has already been briefly described above (p. 79), where its chief 

 characteristics have been given. To these may here be added that it 

 yields no colouration with iodine, is very feebly dextrorotatory and 

 appears to form a compound with cupric oxide ; the latter is obtained 

 when caustic soda and sulphate of copper are added to its solution, 

 and may be used for the separation of animal-gum from urine 3 . 



5. Glycogen (0 6 H 10 O 5 ) n . 



This substance is from a purely chemical point of view extremely 

 like starch, the similarity being most marked when the hydrolytic 

 products of the two are compared. A study of its occurrence, 

 behaviour and fate in the animal body leaves but little doubt that it 

 may be regarded from the physiological side as truly the animal 

 analogue of the vegetable starch, and as such it is frequently spoken 

 of as ' animal starch.' It was first described as a constituent of the 

 liver by Bernard 4 and, simultaneously though independently, by 

 Hensen 5 . In more recent times it has been found to occur in greater 

 or less quantities in many tissues of the adult body, as for instance the 



1 Lea, Jl ofPhysiol Vol. xi. (1890), p. 226. 



2 But see Wohl, Ber. d. d. chem. Gesell, Jahrg. xxm. (1890), S. 2101. 



3 Landwehr, Central!), f. d. Med. Wiss., 1885, S. 369. See also Wedenski, Zt. 

 f. physiol. Chem. Bd. xm. (1889), S. 122. 



4 Gaz. med. de Paris, 1857, No. 13. Compt. Rend. T. XLIV. (1857), p. 579. Gaz. 

 Hebdom. 1857, No. 28. 



5 Arch. f. path. Anat. u. Physiol. Bd. xi. (1857), S. 395. 



