ARTERY. 



225 



the station which the principal trunk had held 

 in the circulation while in its normal condition. 

 Several distinguished anatomists and physiolo- 

 gists have considered the property of elasticity 

 of the arteries sufficient to account for all the 

 phenomena of the circulation of the blood 

 through these vessels. This opinion has been 

 principally insisted on by Haller, Bichat,Nysten, 

 and, at the present day, by Magendie; elasticity, 

 however, can only account for contractions 

 taking place in consequence of previous dis- 

 tension, and is equally evident after death as 

 during life : but observation and experiments 

 have shewn that, in the living body, the arteries 

 possess an additional power of contraction, by 

 which their calibre may be diminished in various 

 degrees ; in some instances even almost to 

 obliteration. And this power of contraction 

 has been considered by many anatomists to 

 indicate the existence of a property of irritability 

 in the arteries, similar to, if not identical with 

 muscularity. The existence of irritability in 

 the arteries was denied by Haller in conse- 

 quence of his not having succeeded in render- 

 ing it evident by the application of chemical or 

 mechanical stimuli. Bichat, Nysten, and Ma- 

 gendie, embraced a similar opinion, on the 

 strength of the following facts : mechanical or 

 chemical stimuli, even the galvanic fluid, ap- 

 plied to the surfaces of the arteries, produce no 

 motions ; when the fibres of the middle tunic 

 are dissected off in successive layers in living 

 animals, they are not observed to display that 

 quivering motion visible among the fibres of 

 muscles similarly treated. When cut longi- 

 tudinally, the inner surface of the arteries does 

 not become everted like that of canals, such as 

 the intestines, which have a decidedly muscular 

 tunic : they do not contract when separated 

 from the heart. The finger introduced into a 

 living artery is not constricted; stimuli applied 

 to the nerves of particular arteries, or to the 

 nervous system generally, do not produce con- 

 tractions; strong acids applied to arteries pro- 

 duce a corrugation or crisping of their struc- 

 ture, not a contraction, like that of muscular 

 structure. 



The contrary opinion as to the existence of 

 irritability in the arteries has been maintained 

 by some of the most distinguished and accurate 

 anatomists and physiologists, among whom are 

 Hunter, Scemmerring, andVerschuir. It may be 

 stated in a general manner, as an objection to 

 the arguments of Bichat, founded on the circum- 

 stance of the arteries not having contracted 

 when stimuli were applied to them in some 

 experiments which he performed, that other 

 irritable parts, even the muscles themselves, do 

 not at all times contract on the application of 

 stimuli. In fact, most of the experiments de- 

 tailed by Bichat, as proving the absence of 

 irritability in arteries, have been performed by 

 Hunter, Verschuir, and Hastings, and with 

 results directly contrary to those obtained by 

 that very distinguished anatomist. Verschuir* 

 found that the arteries contracted when stimu- 



* Dissertatio de artcriarum ct venarum vi irrita- 

 bili. Gronigen 1766. 

 VOL. I. 



lated by the mineral acids, by electricity, and 

 the application of the point of a scalpel. Dr. 

 Thomson* also saw them contract on the ap- 

 plication of ammonia, and when punctured 

 with the point of a fine needle in the living 

 body. Irritating the nerves by the galvanic 

 fluid or by caustic alkalies has been fol- 

 lowed by contraction of the arteries.f Mr. 

 Hunter}; found that the exposure of arteries to 

 the air was followed by their contraction to 

 such an extent as to produce their obliteration. 

 An instance of this we have twice witnessed 

 in the brachial artery when exposed during the 

 progress of an operation for traumatic aneurism 

 at the bend of the elbow. The contraction 

 of divided arteries is well known to be an 

 efficient means of arresting haemorrhage, in op- 

 position to the force with which the blood 

 is propelled through them by the heart's 

 action. 



In conclusion, we may observe that the 

 arteries are proved to be both elastic and 

 irritable ; that elasticity predominates in the 

 large trunks, and irritability in the smaller 

 branches ; that their irritability, like that of 

 muscles, is under the influence of the nervous 

 system, and obeys the immediate application 

 of chemical and mechanical stimuli, the effects 

 of which must, however, be very much modified 

 by the influence of the elasticity with which 

 they are endowed. (See CIRCULATION.) 



In men the arteries are said to have their 

 tunics thicker, and to possess greater density 

 and a higher specific gravity than in women. 

 The arteries are larger, more numerous, and 

 their coats are softer in young persons : they 

 become more fragile, and their elasticity di- 

 minishes, in advanced life. 



In the progressive development of parts the 

 arteries appear before the heart; but in the 

 chick, during its evolution, the veins of the yolk 

 precede them in their development, as ascer- 

 tained by the researches of Malpighi, IIaller,|| 

 Wolff,H Pander,** and Rolando.ft 



BIBLIOGRAPHY. Hebenstrcit, Progr. de artc- 

 riavum corp. human, confiniis, 4to. Lips. 1739 

 (Rec. in Mailer's Coll. Disp. Anat. vol. ii.) ; Ejns, 

 Progr. de vaginis vasovum, 4to. Lips. 1740 (Rec. in 

 Haller, &c. vol. ii.); Ejus, Progr. de flexu arteri- 

 arum, 4to. Lips. 1741 (Rnc. in Haller, &c. vol. ii.) 

 Monro, on the coats of arteries and their diseases, in 

 Ej. Works, 4to. Edinb. De la Sone, Sur la structure 

 des arteres in Mem. de Paris, 1756 and 1762. 

 Van Swieten, De arterioe fabrica et efficacia incorp. 

 human. 4to. Lugd. Bat. 1725. Alblnus, De arteriae 

 membranis et vasis in Ej. annotat. academic, lib. iv. 



* Lectures on Inflammation. Edinburgh, 1813. 

 p. 75-89. 



t Vide a paper by Sir E. Home on the Influence 

 of the nerves upon the action of arteries, Philoso- 

 phical Transactions for 1814. 



f Treatise on the Blood, p. 114. 



$ De formatione pulli in ovo. 



[i Opera Minora, t. ii. 



Ii Theoria Gcnerationis. 



** Journal de Progres des Sciences et des In- 

 stitut. Medicales, t. v. and Journal de Physique, 

 t. Ixviii. also his Beitriige zur Entwickelungsges- 

 chichte des Hum-lions im Eie. Wiirtzburg, 1817. 



ft Journal C'omplementaire du Diet, des Sc. 

 M6d., t. xi. p. 323, et t. xii. p. 34. 



Q 



