: -: . 



CM KMISTKY. 



[DIOHTIO*. 



soluble and <~f>tgnlV(rl vegetable albumen has not yet 

 been determined ; but the quantity of sulphur and phos- 

 phorus is always very small in comparison with that of 

 the other clement*. 



Amongst the albuminous principles, soluble vegetable 

 .,'.. IBHL ' uninc, . inn n d t Mood. ...'' D :i ' : 

 eggs, globuhue and caseine, are, when fresh, soluble in 

 water; the principle of the yolk of eggs dissolves with 

 great difficulty ; coagulated vegetable albumen, gluten, 

 and fibrine of the blood, not at all The different kinds 

 of albumen, in a stricter sense, coagulate if boiled in 

 water, at everybody has seen in hard-boiled eggs. The 

 globuline of blood coagulates by warmth alone ; legu- 

 luiuc and caieiue by acids in a warm temperature, 

 ..now how quickly milk curdles and turns sour in 

 warm weather. 



All albuminous principles, insoluble as well as soluble, 

 are. in a coagulated state, dissolved at a somewhat 

 higher temperature by a solution of potash, and 

 frvui this solution, precipitated by acids in a solid form. 



5 7. Digtttion. After this brief description of the 

 most important alimentary principles comprising our 

 nutriment, wo shall resume the account of digestion. 



The whole of digestion is included under two grand 

 processes. First, the alimentary principles must be dis- 

 r very minutely divided ; and secondly, if 

 different from the constituents of blood, they must be 

 formed into these. Let us now see how these 

 changes take place by the action of saliva, gastric juice, 

 pancreatic, and intestinal juice, upon the com- 

 pounds of chlorine, the salts, the constituents of fat, the 

 tatty substances, and albuminous matter. 



All fluids which flow to the digestive organs contain a 



. vely largo quantity of water, at a temperature of 



08 Fah. Common salt and chloride of potassium are 



easily dissolved iu this water, as well as the phosphoric, 



sulphuric, and carbonic alkaline salts. 



In thu liquid of the gastric juico is a free acid. The 

 earthy salts, therefore, which we before described as 

 hardly or not at all soluble in pure water, but easily 

 so in acid, are by this means reduced to a dissolved .- 



Owing to the higher temperature peculiar to ah 1 the 

 fluids of our body, a part of fluoride of calcium is dis- 

 solved ; but the greater part of it, and of the oxide of 

 in. u, remains undissolved. This explains why the 

 alviiie evacuations always contain so much iron. Here 

 also the gastric acid plays an important part, inasmuch 

 as it dissolves a portion of the iron, which is thoroughly 

 usable to the blood. 



Starch by itself is not soluble in the water of the 

 digestive fluids ; but saliva, the mucus of the mouth, 

 pancreatic and intestinal juice, have, in combination 

 with each other, in a remarkable degree, the property of 

 transmuting starch into gum, and gum into sugar. 

 Thus, starch is not only indirectly dissolved, but U sub- 

 jected in that process to such changes as render it capa- 

 ble of Wing assimilated with thu substances of the 

 blood; for sugar is transformed into lactic acid by the 

 action of the bile ; lactic acid into butyric acid while 

 progressing through the alimentary canal ; ami butyric 

 acid is the tint link in the series <.f fatty principles 

 which are f .und in living bodies. Oleic and margaric 

 acid dilk-r in their composition from butyric acid only 

 by containing more carbon and hydrogen in proportion 

 . r oxygen. 



The but effect of digestion upon all the constituents of 

 fat in transmutation into fat itself. Starch and gum are 

 transformed into sugar, sugar into lactic acid, lactic 

 acid into butyric acid, and butyric acid into other fatty 

 substance*. 



d fats are principally digested by the action of 

 pancreatic juice, assisted by the bile. These fluids divide 

 tin.- fat into particles so small, as to bo capable of riasily 

 penetrating through the membranes moistened l.y thu 

 bile. Another smaller portion of the fat is actual I . 

 solved, for the carbonic alkali of thu bile first ellccts a 

 spnrinntion of the fat, then the . , . action of 



the pancreatic juico transforms it into fattyjacids and 

 glycerine : thus stearic acid and glycerine arise from 



stearino ; oleio acid and glycerine fro The fatty 



acids combine with the alkalies to form soaps, which 

 are soluble. 



All the fluid* of the digestive canal act at solvents 

 i ho albuminous substances ; and to this dissoh 

 n almost all the components of these fluids Co 

 bute. It U especially so with the free acid of the gastric 

 juice ; in the next place, with the predominating alkali i 

 saliva, bile, pancreatic, and intestinal juice; thru with 

 organic substances, water, and the salts of all 

 juices. By the action of the acid of the gastric juice, i 

 the soluble albuminous substances are first coagulated ; 

 but they are again dissolved by degrees, by means of a 

 power wlu'ch the gastric acid exercises upon undissolved 

 albuminous substances, supported by the alkalies of the 

 intestinal and pancreatic juice. The most important 

 agents in the dissolution of albumiinms matter are, 

 however, the organic components of the gastric and iu- 

 il juices. 



the dissolving action of the digestive juice. 1 !, and 

 by the peristaltic grinding motion i the walls of the 

 digestive canal, food is changed in the stomach into a 

 pulp called chyme. This, by degrees, is rendered more 

 Liquid, until it becomes a thick, milky juice, which 

 ' 'gists call chyle. 



This chyle is essentially a mixture of dissolved com- 

 pounds of chlorine, of salts, sugar not yet entirely i 

 muted into fat, of lactic and butyric acids, of finely di- 

 vided and saponified fats, and of soluble albumen, i 

 also, the latter may be rcgurdtd as representing the 

 ining class of albuminous substances ; and iliis so 

 much the more, as these after-liquefactions h 

 in the highest degree, similar in their properties to 

 soluble albumen; but still they retain their original 

 ition. 



8. The Chylt. Thus the liquefied alimentary prin- 

 ciples flow over the inner surfaces of . inal 

 wall-*, in which are numerous vessels, long and narrow 

 canals with thin walls, into which the greater part of 



milky chyle exudes. These vessels are, tin i 

 called liictcalt. Not only their walls, but also th< 

 the blood-vessels, are permeable by liquids ; and, i 

 fore, a considerable part of the chyle also exudes into 

 tin- bl. tod- vessels of the intestines. 



\Vheu digestion is nearly finished, the laeteals teem 

 with a white milky juice, which owes its colour to the 

 fat they have taken up ; for if no fat have been 

 we find in these vessels only a clear, transparent j 

 scarcely deserving the name of chyle. 



The very numerous and smallest lacteals gradually 

 unite themselves into larger trunks, which, ; 

 ]Kiints, run very m-ar MOB other, repeatedly widening 

 and contracting, something like a string of 1 

 pursuing irregular windings, held together by cellular 

 tissue, and forming, as it were, lumps or knots, which 

 have lieen improperly called intestinal gl.-i; 



The lacteal v. C having passed through these 



knots, by uniting in gradually larger trunks, for; 

 length one duct. By the junction of this trunk with 

 two vessels, which convey a wlui. iluid from 



other parts of the body, and are called alaoi!,, itt.;, an- 

 other canal is formed, which passes through the cavity 

 of the abdomen and chest near tl d column, 



and is called (In- tlmnicic duct; through this the chyle 

 flows into the blood. 



The composition of the chyle, which has been 

 absorbed by the lacteals, dii little from the 



liquid which, during digestion, is contained in the 

 lower part of the sin nes. lie tore 



vessels, in their convolution 

 into knots, the properties of their . 



:ly the same as they were in that part of the i 



from which they were taken. The quantity, how- 

 ever, of solid matter hold iu solution in tin- liquids 

 varies; accordingly, the chyle contains more water in 

 the lacteals tbau in the intestinal canal. This facili- 

 ! tales the transition of matter from the intestinal canal 

 into the lacteals. The water in the latter has a 

 great affinity to the substances which, in a dissolved or 



