134 THE DIGESTIVE FLUIDS. 



be imagined that in such cases, and perhaps even under normal 

 conditions the internal secretion of the gland is removed through 

 the lymph-channels. It has been shown, moreover, that diabetes 

 does not occur after extirpation of the pancreas if a piece of the 

 gland has been previously transplanted under the skin. 



Of the nature of the substance or substances which are thus 

 secreted by the pancreas, and in the presence of which the carbo- 

 hydrate metabolism continues in a normal manner, we know nothing. 

 According to Lupine and his school, the gland is supposed to furnish 

 a glucoly tic ferment, which brings about oxidation of the sugar in the 

 tissues, and it will be seen that such a ferment can actually be demon- 

 strated in the blood. The time has not come, however, when we 

 can speak definitely on this subject. 



The secretion of the pancreatic digestive fluid, like that of the 

 saliva, is partly under the control of cerebrospinal nerve-fibres, which 

 are derived from the vagus, and partly of sympathetic fibres. The 

 material from which the secretion is elaborated through the specific 

 activity of the glandular cells is obtained from the lymph, and ulti- 

 mately, of course, from the blood. In carnivorous animals, in which 

 the secretion of the pancreas is intermittent and dependent upon the 

 ingestion of food, we accordingly find that in its stage of activity the 

 gland assumes a bright rose-color, and is much increased in size, 

 while in the resting stage it is pale and shrunken. 



General Properties. Fresh pancreatic juice can be obtained 

 only by establishing an artificial fistula in. the pancreatic duct. But 

 as the least interference with the integrity of the gland leads at once 

 to the secretion of an abnormal fluid, great care must be exercised 

 to operate as gently and rapidly as possible. It is best to do so 

 about three hours after the animal has received a large meal. For 

 a short while at least, a normal secretion can then be obtained. This 

 represents a clear, thick, colorless and odorless, very concentrated 

 fluid, of a strongly alkaline reaction, which actively digests albumins, 

 inverts starches and the more complex sugars, and emulsifies fats. 

 After a variable length of time, however, the secretion becomes 

 thinner, more deficient in solids, and otherwise altered, so that it 

 can scarcely be regarded as normal. 



Specific Gravity. The specific gravity of the pancreatic juice 

 varies between 1.008 and 1.010, corresponding in man to the pres- 

 ence of from 2.5 to 7 per cent, of solids. When kept for a few 

 hours at ordinary temperatures it loses its viscosity and transparency, 

 and rapidly undergoes putrefaction. Crystals are then deposited 

 which consist of leucin and tyrosin ; they result from the digestion 

 and subsequent decomposition of contained albumins. To prevent 

 these changes, the secretion must be placed on ice at once, or treated 

 with chloroform-water or a similar antiseptic solution. Owing to 

 the presence of the large amounts of albumin which the pancreatic 

 juice contains, the liquid coagulates to a dense mass when heated to 

 a temperature of 74 C. On cooling to C., or when dropped into 



