Volume 1

A text-book of human physiology : including histology and microscopical anatomy with special reference to the requirements of practical medicine / by L. Landois ; translated from the seventh German edition with additions by William Stirling.

Landois, L. (Leonard), 1837-1902. Lehrbuch der Physiologie des Menschen. English

Date:: 1891

Credit: A text-book of human physiology : including histology and microscopical anatomy with special reference to the requirements of practical medicine / by L. Landois ; translated from the seventh German edition with additions by William Stirling. Source: Wellcome Collection.

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$to the diminished alkalinity, and this is in part owing to the acid products formed during the decomposition of the tissues.] III. Nitrogen exists in the blood to the extent of 1-4 to 1-G vol. per cent., and it appears to be simply absorbed. It is doubtful if any part of the N exists chemically united in the r^d corpuscles. Blood warmed outside the body, and with a free supply of oxygen, gives off a minute quantity of ammonia,which is perhaps derived from the decomposition of some salt of ammonia as yet unknown {Kühne and Strauch). 39. ARTERIAL AND VENOUS BLOOD.—Arterial blood contains in solution all those substances which are necessary for the nutrition of the tissues, those which are employed in secretion, and it also contains a rich supply of 0, and, as we have seen, a considerable amount of COg. Venous blood contains less of the nutrient matter, but in addition it holds the used-up or effete substances derived from the tissues, and the products of their retrogressive metabolism are more numerous ; there is in venous blood a larger amount of COj, and also a considerable amount of 0. [The fundamental difference between Arterial and Venous blood is due to the relative proportion of oxygen and carbon dioxide contained in each. The difference in colour depends on this. If venous blood be shaken up with air or oxygen it becomes arterial, while if arterial blood be submitted to a current of an indifferent gas such as N or H, it becomes venous. It also does so if it be sealed up in a vessel for some time, whereby the oxygen is used up, and gradually more and more of the oxyhsemogiobin is changed into reduced haemoglobin.] It is evident also that the blood of certain veins, the portal and hepatic, must have special characters. The following are the most important points of difference between arterial blood and venous blood :— Arterial Blood contains— more salts, It is redder and not more fat, more sugar, fewer blood-corpuscles, less urea. dichroic. As a rule it is 1° C. warmer. It coagulates more rapidly. more 0, less CO, more water,j^-— ^ more fibrin, more extractives, The bright red colour of arterial blood depends on the presence of oxyhsemo- globin, whilst the dark colour of venous blood is due to its smaller proportion of oxyhsemoglobin, and the quantity of reduced haemoglobin which it contains. The dark change of colour is not to be attributed to the larger quantity of CO^ in venous blood {Marchand); for if equal quantities of 0 be added to two portions of blood, and if COg be added to one of them, the colour is not changed {Pflüger). [According to C. Schmidt, the blood of the portal vein contains more water, plasma, salts, and fats, but less extractives and corpuscles than the blood of the hepatic vein ; while (when an animal is not digesting) sugar is absent, or at least only in traces in the portal vein, and in considerable amount in the hepatic vein (§ 175).] [Blood of the hepatic vein is said to contain more corpuscles than that of the portal vein, and it is supposed not to coagulate after death, but this is very^ doubt- ful. According to Drosdoff, it contains more water, Cholesterin, and lecithin than the portal vein except during digestion ; it also contains more sugar, and it is the warmest blood in the body.] [Splenic Vein.—Some observers say that this vein contains more, and others fewer, red blood-corpuscles than that of the artery. The statement is also made that it contains more white corpuscles, but this, again, is denied by Tarchanoff. The notion that its serum contains haemoglobin has been disproved by Schäfer. In this latter respect it does not differ from that of serum of blood generally.] [Renal Vein.—Here the blood is bright red, and holds more 0 and less COg than the blood of the renal artery. It contains less water, NaCl, uric acid, and urea, and coagulates with difficulty.]$