RESPIRATION. 



357 



ance of nutrition and secretion than of respi- 

 ration. 



The most marked difference, more espe- 

 cially in warm-blooded animals, between ar- 

 terial and venous blood is that of colour, 

 arterial blood being of a scarlet red, and ve- 

 nous blood of a dark Modena hue. The 

 extent of this difference of colour between 

 the blood in the arteries and in the veins 

 varies in the different vertebrata, and is greater 

 in birds and in the mammalia than in reptiles 

 and fishes ; and it also varies in different con- 

 ditions of the body and surrounding media in 

 the same animal. In animals exposed to 

 artificial high temperatures*, or living in 

 warm climates f, when the energy of the re- 

 spiratory function is naturally diminished, the 

 venous blood may be of a brighter colour 

 than usual, while the arterial may be less so, 

 and it may then be difficult to distinguish the 

 one kind from the other. In certain cases of 

 high febrile excitement of the circulation, as 

 in acute rheumatism when the blood passes 

 rapidly and abundantly through the lungs, the 

 blood in the veins may be of a scarlet colour: 

 on the other hand, where the aeration of the 

 blood is imperfect, as during the state of hy- 

 bernation, in certain diseases, or from some 

 mechanical ; mpediment to the free passage of 

 the air into the lungs, the blood flowing along 

 the arteries approaches more or less the dark 

 colour of venous blood. 



The temperature of the arterial blood in the 

 left side of the heart, aorta, and large vessels 

 springing from it, is higher than the venous 

 blood by from 1 to 2 Fahr., according to 

 Dr. John Davy J, and 1'01 C (1'818 Fahr.) 

 on an average, according to Becquerel and 

 Breschet. According to Dr. Davy, the ca- 

 pacity of venous blood for caloric is 852, that 

 of arterial blood 8.39. || 



The specific gravity of venous is somewhat 

 greater than that of arterial blood. Dr. Davy 

 gives the specific gravity of arterial blood as 

 1050, that of venous as 1053. If Some of 

 those who have published analyses of both 

 kinds of blood, procured more solid materials 

 and less water from venous than from arterial 

 blood ; others again have obtained the oppo- 

 site result; while Denis, in his analysis of the 

 blood of a dog, observed no difference in this 

 respect. The~number of instances, taking 

 the more trust-worthy analyses only into ac- 



* Crawford. Experiments and Observations on 

 Animal Heat, p. 309. 3rd edit. 



f Dr. J. Davy. London Phil. Transact, for 1838, 

 p. 28. 



{ Researches, Physiological and Anatomical, vol. 

 i. p. 147. 1839. At page 211 of the same volume, 

 another series of experiments is given, in which the 

 difference in temperature varied from 1 to 3 F. 



Annales des Sciences Naturelles, 2me serie, torn, 

 vii. p. 94. 1837. Becquerel and Breschet, in their 

 experiments, used a thermo-electric apparatus. They 

 found the difference of temperature between the two 

 kinds of blood diminish as the blood-vessels are more 

 distant from the heart. 



|| Kesearcb.es, Physiological and Anatomical, vol. i. 

 p. 146. 



t Opus cit. vol. ii. p. 22. 



count, where the quantity of water was 

 greater in the arterial than in the venous 

 blood decidedly preponderates. In all pro- 

 bability the relative quantity of water in the 

 two kinds of blood is determined by the rela- 

 tive extent of the loss of that fluid by the 

 arterial blood at the kidneys, lungs, skin, &.c., 

 and of the supply entering the veins from 

 without, but chiefly through the mesenteric 

 veins. 



A larger quantity of fibrin has been ob- 

 tained by some analysts from arterial than 

 from venous blood in man and in the domes- 

 ticated animals; others again have procured a 

 larger quantity from venous than from arterial 

 blood ; while a few have obtained dissimilar 

 results in their analyses of these two kinds of 

 bljod in different genera of animals, and even 

 in different individuals of the same species.* 

 In the greater number of the analyses, however, 

 more fibrin was obtained from arterial than 

 from venous blood, -j- According to Denis and 

 Scherer, the fibrin of the two kinds of blood 

 differs in regard to its solubility in nitre. When 

 a portion ot well-washed fibrin from venous 

 blood is triturated with a third part of nitre, 

 and four times its weight of water, and a 

 small quantity of caustic potass or soda is 

 then added, it dissolves into a gelatinous 

 mass, having the chemical characters of albu- 

 men ; while the fibrin from arterial blood si- 

 milarly treated undergoes no such changes. 



The blood-corpuscles are more abundant 

 in arterial than in venous blood, according to 

 Prevost and Dumas, Lecanu and Denis ; ac- 

 cording to Meyer, Hering, and Nasse, they 

 are more abundant in the venous blood ; 

 while the analyses of Letellier and Simon 

 tend to show that the proportion is fluctu- 

 ating. According to Simon, the blood-cor- 

 puscles of arterial contain less haematin than 

 venous blood, while the quantity of globulin 

 is variable. Mulder states that the chemical 

 composition of hsematin is the same whether 

 derived from arterial or venous blood. J 



The statements made regarding the relative 

 proportions of the albumen, fat, osmazone, 

 and salts in the two kinds of blood, differ too 

 much to justify us in attaching any importance 

 to them, a remark which, as yet, we are 

 afraid applies with too much truth to most 

 of the other statements regarding the che- 

 mical differences between the two kinds of 



* Xasse (article Blut, in Wagner's Handwb'rter- 

 buch der Physiologie, Band i. S. 171) states that 

 the difficulty of conducting a correct quantitative 

 analysis of the fibrine of the blood is sufficient to ac- 

 count for these discrepancies. 



f We refer those who may wish to obtain more 

 detailed information upon this and some other points 

 connected with the chemical differences between 

 the arterial and venous blood, with references to 

 the different authors who have investigated this 

 subject, to Nasse's Treatise, entitled Das Blut, &c., 

 and the article by him in Wagner's HandwiJrter- 

 buch already referred to, and the first volume of 

 Simon's Animal Chemistry, translated for the Sy- 

 denham Society, by Dr. Day. 



J The Chemistry of Vegetable and Animal Phy- 

 siology. Translated from the Dutch by Fromberg. 

 Part II. p. 334. 



A A 3 



