HARVEY'S CHEMISTRY. 23 



mixture of blood from various parts of the body. After describ- 

 ing the intestinal veins, Harvey says : '* The blood returning by 

 these veins and bringing the cruder juices along with it, on 

 the one hand from the stomach, where they are thin, watery, 

 and not yet perfectly chy lifted ; on the other, thick and more 

 earthy, as derived from the fteces, but all pouring into this 

 splenic branch, are duly tempered by the admixture of con- 

 traries."* 



Harvey's chemical expressions are crude, for cliemistryas a 

 science only began to exist about a century and a half after 

 Harvey's death, yet the general idea which he expresses in the 

 words which I have just quoted is wonderfully near the truth. 

 . Two of the most important constituents of tlie blood are 

 chloride of sodium and water. Chloride of sodium is a neutral 

 salt, but during digestion both it and water are decomposed in 

 .the gastric glands, and hydrochloric acid is poured into the 

 stomach, while a corresponding amount of soda is returned into 

 the blood, whose alkalinity increases pari passu with the acidity 

 of the stomach. Part of this alkali is excreted in the urine, so 

 that the urine during digestion is often neutral or alkaline. 

 Possibly some of it passes out through the liver in the bile, and 

 through the pancreas and intestinal glands into the intestine, 

 where, again mixing with the acid chyle from the stomach, 

 neutralisation takes place, so that neutral and comparatively 

 inactive chloride of sodium is again formed from the union of 

 active alkali and acid. But it is most probable that what occurs 

 in the stomach occurs also in the other glands, and that the 

 liver, pancreas and intestine do not merely pour out the excess 

 of alkali resulting from gastric digestion, but' that these glands 

 also decompose neutral salts, pouring the alkali ' out through 

 their ducts, and returning the acid into the blood. 



We are now leaving the region of definite fact and passing 

 into that of fancy, but the fancies are not entirely baseless, and 

 may show in what directions we may obey Harvey's behest to 

 search out and study the secrets of nature by way of experi- 

 ment. For what is apparently certain in regard to the decom- 

 position of chloride of sodium in the stomach, and probably in 



* The Worlcs of William TTarr^?/, SrVl(5fTVT>ih'r(-R-icintv's e.lition.. p. 75. 



