344 SECRETION OF PANCREATIC JUICE. 



the lacteals. If the fat to be emulsified contains a free fatty acid, i.e., if 

 it be slightly rancid, and if the fluid with which it is mixed be alkaline, emulsifi- 

 cation takes place extremely rapidly (Briicke). A drop of cod-liver oil, which in 

 its unpurified condition always contains fatty acids, on being placed in a drop of 

 0'3 p.c. solution of soda, instantly gives rise to an emulsion (Gad). The exces- 

 sively minute oil globules that compose the emulsion are first covered with a 

 layer of soap, which soon dissolves, and in the process small globules are detached 

 from the original oil globules. The fresh surface is again covered by a soap film, 

 and the process is repeated over and over again until an excessively fine emulsion 

 is obtained (G. Quincke). If the fat contain much fatty acid and the solution of 

 soda be more concentrated, "my din-forms" are obtained similar to those which 

 are formed when fresh nerve-fibres are teased in water (Briicke). Animal oils 

 emulsionise more readily than vegetable oils; castor oil does not emulsionise (Gad). 



[Pancreatic Extracts. The action of the pancreas may be tested by making a 

 watery extract of a perfectly fresh gland. Such an extract always acts upon starch 

 and generally upon fats, but this extract and also the glycerine extract vary in 

 their action upon proteids at different times. If the extract watery or glycerine 

 be made from the pancreas of a fasting animal, the tryptic action is slight or 

 absent, but is active if it be prepared from a gland 4 to 10 hours after a meal.] 



The pancreas of new-born children contains trypsin and the fat-decomposing 

 ferment, but not the diastatic one (Zweifel). A slight diastatic action is obtained 

 after two months, but the full effect is not obtained until after the first year 

 (Korowin). 



IV. According to Kiihne and W. Roberts, the pancreas contains a 

 milk-curdling ferment, which may be extracted by means of con- 

 centrated solution of common salt. 



171. The Secretion of the Pancreatic Juice. 



As in other glands, we distinguish a quiescent state, during which 

 the gland is soft and pale, and a state of secretory activity, during 

 which the organ swells up and appears pale red. The latter condition 

 only occurs after a meal, and is caused probably in a reflex way owing 

 to stimulation of the nerves of the stomach and duodenum. Kiihne 

 and Lea found that all the lobules of the gland were not active at 

 the same time. The pancreas of the herbivora secretes uninterruptedly 

 [but in the dog, secretion is not constant]. 



Time of Secretion. According to Bernstein and Heidenhain, the 

 secretion begins to flow when food is introduced into the stomach, and 

 reaches its maximum 2-3 hours thereafter. The amount falls to- 

 wards the 5th or 7th hour, and rises again (owing to the entrance of the 

 chyme into the duodenum) towards the 9th and llth hour, gradually 

 falling towards the 17th-24th hour, until it ceases completely. When 

 more food is taken the same process is repeated. As a general rule, 

 when the secretion occurs rapidly it contains less solids than when it 

 takes place slowly. 



Condition of Blood-vessels. During secretion, the blood-vessels 

 behave like the blood-vessels of the salivary glands after stimulation of 



