VEIN. 



1367 



Batav. 18381843. Sclwmburgk, On British Guiana, 

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 Languages of the North-West Coast of America, in 

 the Journal of Geogr. Soc. 1842. Dr. Andrew Smith, 

 Report of the Expedition for Exploring Central 

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 183(). Soemmtring, Uber die Korperlich Vers- 

 chiedenheit desNegers vom Europeens, Mainz, 1784. 

 Sonniai, Travels in Egypt (transl.), London, 1799. 

 Sparrman, Voyage to the Cape of Good Hope and 

 round the World, Perth, 1789. Sp!x und Marlins, 

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 Continuation of Adelung's Mithridates, Berlin, 1806 

 1817. Yergleichungstafeln der europiiischen 

 Stamm-Sprachen, Berlin, 1822. Virey, Histoire 

 Naturelle du Genre Humain, Paris, 1824.. Volncy, 

 Voyage en Syrie et en Egj'pte, Paris, 1787. Wilkes, 

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 London, 1803. 



W. B. Carpenter. 



VEIN (*\<ty, Gr.; Vena, Lat. ; Vehie, Fr. ; 

 BIntader,Ger.', Vena, Ital.; Vena, Span.). In 

 general anatomy the term vein, in the higher 

 animals, includes four sets of blood-vessels, 

 differing in so many respects from each other 

 as to render it difficult to give a general defini- 

 tion which shall include all under one head, 

 either as it regards structure, course, or func- 

 tion : indeed, so unlike are the different sys- 

 tems of veins, that the only remark which can 

 he said to apply to them all is, that they convey 

 blood in a direction towards the heart ; in this 

 respect, as well as in their want of uniformity 

 of character, being directly opposed to the 

 arteries. 



The four systems of veins are the systemic, 

 the portal, the pulmonary, and certain veins 

 peculiar tojcetal life thu ductus venosus and 

 umbilical vein ; and it will be found, upon 

 contrasting them, that they differ much from 

 each other, considering that all enjoy the 

 common appellation vein. Thus, the systemic 

 veins, which correspond to the branches of 

 the aorta, excepting those of the abdominal 

 viscera, collect the blood from small and nu- 

 merous vessels into larger and fewer in its 

 progress towards the heart, constituting a 

 course of circulation of a truly venous cha- 

 racter ; while, on the other hand, that portion 

 of the blood, which is conveyed to the ab- 

 dominal viscera by the branches of the ab- 

 dominal aorta, is first collected from numerous 

 branches into one vessel the vena porta 

 thus far the circulation being venous, and is 

 then again broken up into smaller and re- 

 dividing vessels, after the manner of ar- 

 teries, and forming, as regards this particular, 

 an arterial circulation, though the vessels 

 are nevertheless veins. In both these in- 

 stances the blood conveyed by the vessels 

 in question has a similar quality, which is 

 characteristic of veins, and is called venous ; 

 it is blood saturated with carbon. In the 

 two other systems of venous circulation 

 the pulmonary and umbilical the current is 



venous while the fluid is arterial, these vessels 

 being channels by which the blood is returned 

 to the heart after it has left the arterialising 

 organs. Again, as regards the structure and 

 calibre of veins, our definition is necessarily 

 loose ; for, while veins are, in a general way, 

 thin, less elastic, and distensible, as contrasted 

 with arteries, they are nevertheless very 

 varied in these particulars in different regions, 

 and though, for the most part, the calibre of 

 veins is greater than that of the corresponding 

 arteries, still this is not always the case, as is 

 found upon contrasting the area of sections of 

 the pulmonary arteries and veins. It is there- 

 fore ini] ossible to give a succinct, and, at the 

 same time, a comprehensive definition of 

 vein ; and the one which appears to me to be 

 most applicable and to include the members of 

 each venous system is this that a vein is a 

 blood-vessel, neither artery nor capillary, convey- 

 ing blood in a direction towards the heart, having 

 walls of greater tenuity and extensibility and, at 

 the same time, less elasticity than an artery. 



The literary history of this subject is chiefly 

 interesting as referring to veins, in their rela- 

 tion to the general circulation. Until the 

 time of Harvey's great discovery, the general 

 physiological relationship of the veins was 

 not understood, and the most discrepant 

 notions were entertained. 



Hippocrates, in none of his writings, draws 

 distinction between arteries and veins. Plato, 

 in his Timasus, describes the veins as con- 

 nected with tlie heart, and receiving blood 

 from it. He regards the veins as the messen- 

 gers, transmitting to the whole body the orders 

 coming from the soul : he attributes to them 

 the functions of sentient and motor nerves. 

 He considers that the veins have two centres 

 the heart and the liver ; and he makes no 

 distinction between them and arteries. Praxa- 

 goras taught that the veins were blood-vessels, 

 in contradistinction to the arteries which he 

 considered air-vessels. Aristotle drew no 

 distinction between arteries and veins. Hcro- 

 pliihts describes both arteries and veins as 

 blood-vessels : but he expresses himself in 

 doubt, as to whether the veins arise from the 

 heart or the liver. Erasistraius, holding the 

 same general doctrines as Pra.ragoras, further 

 described the texture of veins very minutely, 

 and, according to Marx, he noticed the ex- 

 istence of valves. Ce/sits and Aretceits made 

 no advance in this subject. Galen distin- 

 guished between arteries and veins both 

 blood-vessels : he also observed the anasto- 

 moses of each : he staled the origin of veins to 

 be from the liver, and of the arteries from the 

 heart, and that both were destitute of sensa- 

 tion. Avicenna described the veins " venas 

 qnietse," in contradistinction to the arteries, 

 which he styled " ventc pulsantes et audaces." 

 According to Baulinus, Avicenna described 

 the valves of veins under the name of "cel- 



The European anatomists of the 15th, 16th 

 and the early part of the 17th century, re- 

 mained in a state of great confusion and ig- 



4 s 4 



