242 DIGESTION. [CHAP. xxv. 



formation of white chyle, and Tiedemann and Gmelin had long 

 since found, that the quantity of fibrine contained in the lymph and 

 chyle, after a long fast, is not less than that which is found there 

 after digestion. Bouchardat and Sandras obtained the same results 

 in their experiments on animals fed on albumen, casein, or gluten, 

 as on animals fed with fibrine \ these substances, therefore, must 

 likewise be excluded from the list of those which are capable of 

 forming chyle. Hence the whole class of neutral azotised sub- 

 stances, admitting of solution by pepsine, may be absorbed without 

 passing into the state of chyle. 



Neither does it appear to be necessary for the appropriation of 

 amylaceous aliments, that they should pass into the condition of 

 chyle. These substances are but little digested in the stomach, 

 and undergo their principal changes in the small intestines. Here 

 the pancreatic fluid exercises a similar influence upon them to that 

 which the neutral azotised matters experience from the gastric 

 juice. Bouchardat and Sandras found that a few drops of pan- 

 creatic fluid, added to some boiled starch, and kept at the tem- 

 perature of from 95 to 104, dissolved it in a short time, the liquid 

 became transparent, and all trace of starch disappeared. The same 

 effect is produced if a piece of the pamcreas be used instead of the 

 pancreatic fluid.* 



The starch in these experiments is converted into dextrine, or 

 into sugar, in which state it is soluble, and thus admits of direct 

 absorption into the blood-vessels, or the sugar undergoes a further 

 change into lactic acid, and in this condition passes into the circu- 

 lation. It appears that the presence of a free alkali is as necessary 

 for these changes, as that of acid is needed for the sohition of the 

 neutral azotised substances. If the pancreatic fluid be acidulated, 

 it ceases to act on starch, but, according to Bernard and Barreswil, 

 acquires the power of dissolving albumen, fibrine, etc. We do not, 

 however, find that alkalized pepsine is capable of dissolving amy- 

 laceous matters. 



Bouchardat and Sandras have examined the changes which 



* Dextrine is a substance having some of the properties of gum, and ob- 

 tained from starch by the action of heat, diastase, or dilute acids. It is 

 soluble in water, and exists in almost every part of plants. When starch is 

 boiled in water for some time an abundance of dextrine is produced. If the 

 action of diastase or of the acids be continued too long, or if the quantity of 

 either be too large, grape-sugar is produced. Hence dextrine may be regarded 

 as the first stage in the transformation of starch into sugar. The formula for 

 dextrine is C 12 H 10 O. See Mulder's Chemistry of Animal and Vegetable 

 Physiology, by Johnston, p. 224, 



