96 THE BLOOD. 



Portal vein. The blood which the portal vein conveys 

 to the liver is supplied from two chief sources ; namely, 

 that in the gastric and mesenteric veins, which contains 

 the soluble elements of food absorbed from the stomach 

 and intestines during digestion, and that in the splenic 

 vein ; it must, therefore, combine the qualities of the 

 blood from each of these sources. 



The blood in the gastric and mesenteric veins will vary 

 much according to the stage of digestion and the nature 

 of the food taken, and can therefore be seldom exactly the 

 same. Speaking generally, and without considering the 

 sugar, dextrine, and other soluble matters which may 

 have been absorbed from the alimentary canal, this blood 

 appears to be deficient in solid matters, especially in red 

 corpuscles, owing to dilution by the quantity of water 

 absorbed, to contain an excess of albumen, though chiefly 

 of a lower kind than usual, resulting from the digestion 

 of nitrogenized substances, and termed albuminose, and 

 to yield a less tenacious kind of fibrin than that of blood 

 generally. 



The blood from the splenic vein is probably more definite 

 in composition, though also liable to alterations according 

 to the stage of the digestive process, and other circum- 

 stances. It seems generally to be deficient in red cor- 

 puscles, and to contain an unusually large proportion of 

 albumen. The fibrin seems to vary in relative amount, 

 but to be almost always above the average. The propor- 

 tion of colourless corpuscles appears also to be unusually 

 large. The whole quantity of solid matter is decreased, 

 the diminution appearing to be chiefly in the proportion 

 of red corpuscles. 



The blood of the portal vein, combining the peculiarities 

 of its two factors, the splenic and mesenteric venous 

 blood, is usually of lower specific gravity than blood 

 generally, is more watery, contains fewer red corpuscles, 

 more albumen, chiefly in the form of albuminose, and 



