DIGESTION OF SUGAR. 73 



ollected, however, that sugar itself is only an intermediate or transitory 

 stage, through which the carbohydrate is passing, a consideration which 

 explains the circumstance that it does not occur even in the portal blood 

 to such an extent as might be expected, nor yet in the chyle. Some 

 have been led to infer from these facts that this substance, like gum, is 

 in reality only very tardily absorbed, an opinion which they suppose to 

 be strengthened by the circumstance that glucose or any other kind of 

 sugar, introduced into the jugular vein, runs through the course of the 

 circulation, and is secreted unchanged by the kidneys. But it is to be 

 remembered that portal blood is very different from the proper systemic 

 blood, and that there are many changes, beyond all question, which can 

 take place with rapidity in the former, but which do not take place in the 

 latter. 



Sugar, whether it has been received as an ingredient of the food, or 

 arisen from the metamorphosis of starch, is, as we have said, only a tem- 

 porary form, which passes quickly onward to the state of lactic acid. To 

 this we must impute the acid reaction which is observed throughout the 

 length of the small intestine, and which can not be attributed to the gas- 

 tric juice, a reaction occurring in spite of the alkalinity of the bile and 

 pancreatic secretion. This pushing of the carbohydrate forward to the 

 state of lactic acid is very generally imputed to the intestinal juice, which 

 greatly re-enforces the power of the saliva and pancreatic fluid; some have 

 even supposed that the bile aids in producing this effect. Of this, how- 

 ever, there is no satisfactory proof. 



From the experiments of Von Becker, who injected saccharine solu- 

 tions at intervals of a quarter of an hour into the stomach of rabbits, it 

 was found that 4.5 parts of sugar were absorbed each hour for every 1000 

 parts weight of the animal. Whatever may have been the form of sugar 

 administered, as, for instance, cane-sugar, it quickly passes into the con- 

 dition of glucose in the intestine, and from that to lactic acid. Thus sug- 

 ar of milk may be traced in an hour as far as the coecum, communica- 

 ting to the contents of the small intestine an intense acid reaction. 



Since lactic acid discharges very important offices in the animal econ-. 

 omy, it may be worth while to observe its properties, and p roduct i onand 

 the circumstances under which it is produced. Very many properties of 

 liquids containing organic matter yield it abundantly: thus it '' 

 is found in sauer kraut, a preparation of cabbage. It is, however, more 

 conveniently obtained from milk, and hence the term lactic acid. The 

 diluted solution obtained from this source, being concentrated by evap- 

 oration, furnishes a sirupy liquid, heavier than water, having an intense- 

 ly sour taste, a great affinity for water, and therefore attracting it from 

 the air, and dissolving freely in it. With metallic oxides it forms solu- 

 ble salts, and in the concentrated sirupy state has the remarkable con- 



