TISSUES OF THE BODY. 123 



1. Arterial and venous Hood. The usual manner of examining these 

 is to compare blood taken from a vein of the skin with that from an 

 artery, consequently only one kind of venous blood. It is generally sup- 

 posed that arterial blood coagulates more rapidly on the whole, and is 

 richer in tibrin, extractives, water, and salts, than the venous, but does 

 not come up to the latter in its amount of albumen and fats. However, 

 we must not give too much weight to this. According to Lehmann, the 

 smaller veins contain more fibrin and water, but less cells, than the arte- 

 ries. The same observer found that the corpuscles of arterial blood have 

 more hseniatin and salts, but far less fats, than those of the venous fluid. 

 Again, arterial blood possesses, in comparison to the remaining gases, more 

 oxygen, while venous is richer in carbonic acid : the corpuscles of the first 

 of these appear red, those of the latter more or less greenish. Venous 

 blood is dichroic, when in thick layers it is dark red, and in thinner green 

 (JBrucke). A solution of reduced haemoglobin manifests the same dichroic 

 properties, whilst oxyhaemoglobin is monochromatic. 



2. Blood from the vena porta and hepatic vein. It has been already 

 remarked above ( 70) that fewer colourless cells appear in the vena porta 

 than in the hepatic vein. The cells, likewise, of the latter seem to differ 

 from those of the remaining kinds of blood, and especially from those of 

 the V. portai ( 67). Finally, no fibrin separates from the blood of the 

 hepatic vein, according to Lehmann (a statement which is, however, ques- 

 tioned), while the vena porta does yield ordinary fibrin. This investigator 

 directed his chemical inquiry towards the blood of horses and dogs, and 

 obtained as a result a much greater richness in cells in the fluid of the 

 hepatic vein, together with a considerable decrease in the quantity of 

 water, consequent on the secretion of the bile. Further, the amount of 

 albumen here is said to be smaller than in the vena porta. In conclusion 

 (according to Lehmann), the blood of the hepatic vein is poorer in salts 

 and fats, richer, on the contrary, in extractive matters, and especially so 

 in grape sugar. The coloured cells of the hepatic vein are, besides, 

 remarkable chemically for their abundance of solid constituents, but the 

 amount of fat, salts, and iron in them has at the same time undergone 

 diminution. 



3. Blood from the splenic artery and vein. We have already referred 

 to the blood of the splenic vein as that which, anatomically speaking, 

 deviates most from the usual standard of this fluid, in that it possesses a very 

 large contingent of colourless corpuscles ( 70), and contains intermediate 

 forms between the two species of cells. It is, further, remarkable for the 

 more spherical figure of its cells, and the readiness with which crystalliza- 

 tion takes place in it, as we have seen in section 13. Fiuike directed 

 attention also to a somewhat modified form of lymph-corpuscle in this blood; 

 it is of larger size, and filled with fine dark granules. The only real 

 chemical difference, however, which could be distinguished by this observer 

 between this peculiar kind of blood and the ordinary kind of the splenic 

 vein, was a decrease in the amount of fibrin. 



4. Menstrual blood. This blood, which is poured out from the turgid, 

 and probably lacerate'd, vessels of the uterine mucous membrane of women, 

 at intervals of four weeks, during the whole time they are capable of bear- 

 ing, is remarkable, at least frequently, for a deficiency of fibrin. It is sup- 

 posed that the latter has either coagulated already within the uterus, or is 

 prevented from undergoing this change by the admixture of mucus when 

 passing through the internal genital parts. But we are still in want here 



