374 MANUAL OF PHYSIOLOGY. 



proportion to the length of time that has elapsed since the death of 

 the animal, and is minimal, if not nil, if the liver or hepatic blood 

 be taken for examination while the tissue elements are still alive. 

 The peculiar blood of the great portal vein coming from the 

 stomach, intestines an<3 the spleen, has then to pass through a 

 second set of capillaries in the liver, and undergoes such important 

 changes that this organ must be regarded as occupying a foremost 



FIG. 164. 



Diagram of the Portal Vein (p v) arising in the alimentary tract and spleen (), and 

 carrying the blood from these organs to the liver. 



position among the blood glands. Differences of "the utmost im- 

 portance have long been thought to exist between the blood going 

 to and that coming from the liver, and to it has even been attrib- 

 uted paramount utility as a blood elaborator ; but the scientific 

 knowledge of its power in this respect must date from the dis- 

 covery of its glycogenic function. 



