254 PANCREATIC JUICE. [BOOK n. 



this respect it affords a striking contrast to gastric juice. But 

 when they have been previously treated with acid or boiled so 

 as to become converted into actual gelatine, trypsin is able to 

 dissolve them, apparently changing them much in the same way 

 as does pepsin. Trypsin unlike pepsin, will dissolve mucin. Like 

 pepsin, it is inert towards nuclein, horny tissues, and the so-called 

 amyloid matter. 



On Fats pancreatic juice has a twofold action: it emulsifies 

 them, and it splits up neutral fats into their respective acids and 

 glycerine. If hog's lard be gently heated till it melts and be then 

 mixed with pancreatic juice before it solidifies on cooling, a creamy 

 emulsion, lasting for almost an indefinite time, is formed. So also 

 when olive oil is shaken up with pancreatic juice, the separation 

 of the two fluids takes place very slowly, and a drop of the mixture 

 under the microscope shews that the division of the fat is very 

 minute. An alkaline aqueous infusion of the gland has similar 

 emulsifying powers. If perfectly neutral fat be treated with 

 pancreatic juice, especially at the body-temperature, the emulsion 

 speedily takes on an acid reaction, and by appropriate means not 

 only the corresponding fatty acids but glycerine may be obtained 

 from the mixture. When an alkali is present, the fatty acids thus 

 set free form their corresponding soaps. Pancreatic juice contains 

 fats, and is consequently apt after collection to have its alkalinity 

 reduced; and an aqueous infusion of a pancreatic gland (which 

 always contains a considerable amount of fat) very speedily becomes 

 acid. 



Thus pancreatic juice is remarkable for the power it possesses 

 of acting on all the food-stuffs, on starch, fats and proteids. 



The action on starch and on proteids, and the splitting up of 

 fatty acids appear to be due to the presence of three distinct 

 ferments, and methods have been suggested for isolating them. 

 The emulsifying power, on the other hand, is connected with the 

 general composition of the juice (or of the aqueous infusion of the 

 gland), being probably in large measure dependent on the alkali- 

 albumin present. The proteolytic ferment trypsin as ordinarily 

 prepared seems to be proteid in nature and capable of giving rise, 

 by digestion to peptones; but it may be doubted, as in the case of 

 pepsin &c. whether the pure ferment has yet been isolated. There 

 are no means of distinguishing the amylolytic ferment of the 

 pancreas from ptyalin. The term pancreatin has been variously 

 applied to many different preparations from the gland, and its use 

 had perhaps better be avoided. 



The action of pancreatic juice, or of the infusion or extract of 

 the gland, on starch, is seen under all circumstances, whether the 

 animal be fasting or not. The same may probably be said of the 

 action on fats. On proteids the natural juice, when secreted in a 

 normal state, is always active. The glycerine extract or aqueous 

 infusion of the gland, on the contrary, differs at different times; 



