202 CIRCULATING FLUIDS: 



by whipping, and are then allowed to stand, the blood-cor- 

 puscles subside in nearly equal times ; but while they occupy 

 little more than one half of the volume of arterial or ordinary 

 venous blood, in portal blood they form nearly three fourths of 

 the whole volume. 



In portal blood, after the lapse of several hours, a delicate 

 glittering film was formed upon the surface of the serum, which 

 when seen under the microscope was found to contain fat-glo- 

 bules ; I could not however discover any lymph-granules either 

 in the serum or amongst the blood-corpuscles. The arterial 

 and ordinary venous blood, on the contrary, exhibited lymph- 

 granules, but no fat-globules. 



The blood of the vena portse not only contains less fibrin 

 than arterial or ordinary venous blood, but the qualities of 

 that constituent are also difl^erent ; it is not so consistent as 

 ordinary fibrin, and does not separate into the firm, globular, 

 little masses that are obtained by whipping arterial blood. 



Our knowledge of the properties of this blood has been ma- 

 terially increased by the researches of Schultz.^ The follow- 

 ing are his principal conclusions : It is darker than ordinary 

 venous blood, but the diflereuce of tint is sometimes so slight, 

 as to be hardly perceptible. It is darkest in fasting horses, 

 but after a full meal, it becomes brighter. These differences 

 are more striking than those between arterial and venous 

 blood. Common salt, nitre, atmospheric air, and even oxygen, 

 when shaken with the dark blood of the vena portse, have 

 scarcely any effect upon the colour, whereas venous blood 

 would be changed to a brighter red by these reagents. If the 

 blood of the vena portae be not extremely dark^ a slight change 

 is perceptible. 



If a portion of this black blood be treated with a quantity 

 of common salt or nitre sufficient to prevent it from coagu- 

 lating, coagulation may still be induced (although not until after 

 several hours, and then very slightly) by the addition of water, 

 while venous blood similarly treated coagulates in the course 

 of five or ten miniites. 



If the blood is very dark, it sometimes does not coagulate 

 at all; if it is not very dark, it occasionally coagulates in the 

 same time as ordinary venous blood ; the clot, however, is very 



' System der Ciikulation, p. 140. 



