98 PHYSIOLOGY CHAP. 



We shall deal in a later chapter with all that concerns the 

 nature of the different digestive processes effected by the pancreatic 

 enzymes, and the conditions which favour, moderate, or inhibit 

 them the importance, in short, of the pancreatic secretion to the 

 utilisation of food-stuffs in general. 



Besides the pancreatic juice obtained by a temporary or permanent 

 fistula of Wirsung's duct, the digestive activity of the pancreas is tested by 

 making an artificial extract of the organ. This is prepared by grinding up 

 the pancreas, after dissecting away the fat and connective tissue, and drying 

 it in a desiccator over sulphuric acid. The dried residue is then treated 

 with alcohol and ether to remove the remaining fat, and macerated with a 

 1 per cent solution of salicylic acid at 40 C. for 12 hours, 500 c.c. of this 

 solution being used for every 100 grins, dried pancreas. The mass^ is then 

 filtered and squeezed through muslin. The solid material is digested for 

 12 hours at 40 C. in 500 c.c. of a 2'5 per cent solution of sodium carbonate, 

 containing a few drops of an alcoholic solution of thymol to prevent putre- 

 faction. The filtrate is rendered alkaline with the same solution, and also 

 allowed to digest at 40 C. for 12 hours. Both from the solid material after 

 filtering from any undissolved residue, and from the solution, a very active 

 artificial pancreatic extract is obtained. 



From these extracts trypsin can be prepared in a state of comparative 

 purity by Kiihne's method. The extracts are allowed to digest for about a 

 week, when all the proteoses will be transformed into peptones. They are 

 filtered, and ammonium sulphate added to the filtrate to saturation. A fine 

 precipitate results, which carries down all the trypsin. This is dissolved in 

 water and dialysed, to remove the greater part of the ammonium sulphate. 

 The remainder of the sulphuric acid is precipitated as barium sulphate by 

 barium carbonate, and the clear filtrate is precipitated with alcohol. The 

 amorphous precipitate thus found is collected on a filter. 



IX. That the pancreas exerts an internal function in carbo- 

 hydrate metabolism was suspected long ago by clinicians (Frerichs, 

 Cantani, Seegen, Bouchardat, and others), since post-mortem 

 examination of many cases of human diabetes showed profound 

 and varied alterations of this organ. But as little was known at 

 that time about the internal functions of glands, and there was 

 then no suspicion of the existence of such a function in a gland 

 provided with an excretory duct, they attempted to explain the 

 diabetes as an indirect consequence of the altered external 

 function of the pancreas. This gave rise to the hypothesis (to 

 which we must refer, because it is still maintained by certain 

 authors) that the food -stuffs being ill -digested, owing to the 

 absence of the pancreatic enzymes, developed toxic substances 

 which, when reabsorbed, inhibited the normal carbohydrate 

 metabolism. 



It was long before any experiments threw light upon this 

 subject. The first attempts at extirpating the pancreas (Conrad 

 Brunner, 1788 ; Cl. Bernard, 1855 ; Berard and Colin, 1857 ; Senn, 

 1880 ; Martinotti, 1880) either resulted in the death of the animal 

 in a short time, making it difficult to analyse the phenomena, or 

 were so incomplete that no disturbance resulted from them, so 



