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. SECKETION OF PANCREATIC JUICE. 257 



be alkaline, emulsification 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 

 per cent, solution of soda, instantly gives rise to an emulsion {Gad). The excessively 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. If the fat contain much fatty acid, and the 

 solution of soda be more concentrated, "myelin forms" are obtained similar to those which 

 are formed when fresh nerve-fibres are teased, in water. Animal oils emulsionise more readily 

 than vegetable oils ; castor oil does not emulsionise {Gad). [It is extremely difficult to obtain 

 a perfectly neutral oil, as most oils contain a trace of a fatty acid. In fact, if on adding a weak 

 solution of sodic carbonate to oil. or fatty matters, fluid at the temperature of the body, an 

 emulsion is obtained, one may be sure that the oil contained a fatty acid, so that Bernard's 

 view about an " emulsive ferment " being necessary is not endorsed. The fatty acid set free by 

 the fat-splitting ferment enables the alkaline pancreatic juice at once to produce an emulsion.] 



Fat-Splitting Ferment. This is a very unstable body, and must be prepared from the 

 perfectly fresh gland by rubbing it up with powdered glass, glycerine, and a 1 per cent, solution 

 of sodic carbonate, and allowing it to stand for a day or two {Grutzner). [This ferment is said 

 to cause an emulsion of oil and mucilage tinged blue with litmus at 40 C. to become red 

 (Gamgee). In performing this experiment notice that the mucilage is perfectly neutral, as 

 gum-arabic is frequently acid.] 



[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 pancreatic preparations of Benger of Manchester, Savory and Moore, or 

 Burroughs and Welcome, all possess active diastatic and proteolytic properties.] 



[Pancreas Salt. Prosser- James proposes to employ common salt mixed with pepsin, which 

 he calls peptic salt ; and he advocates the use of another preparation composed of the pancreatic 

 ferments and common salt, pancreatic salt.] 



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. The pancreas contains a milk-curdling ferment, which may be extracted 

 by means of a concentrated solution of common salt. 



171. THE SECRETION OF THE PANCREATIC JUICE. Rest and 



Activity. 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 renexly 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 to 3 hours thereafter. The amount falls towards the 5th or 7th hour, and rises 

 ?again (owing to the entrance of the chyme into the duodenum) towards the 9 th 

 and 11th hour, gradually falling towards the 17th to 24th hour until it ceases 

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

 rule, a rapidly-formed secretion contains less solids than one formed slowly. 



Condition of Blood- Vessels. During secretion, the blood-vessels behave like 

 the blood-vessels of the salivary glands after stimulation of the chorda they 

 dilate, and the venous blood is bright red thus, it is probable that a similar 

 nervous mechanism exists, [but as yet no such mechanism has been discovered]. 

 The secretion is excreted at a pressure of more than 17 mm. Hg. (rabbit). 



Effect of Nerves. The nerves arise from the hepatic, splenic, and superior 

 mesenteric plexuses, together with branches from the vagus and sympathetic. 

 The secretion is excited by stimulation of the medulla oblongata, as well as by 

 direct stimulation of the gland itself by induction-shocks. [It is not arrested by 



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