216 



ARM. 



The general result of these observations, and 

 of many others of the same kind, is, 1st, that 

 the legs of spiders can be reproduced when 

 they have been torn off; 2d, that this repro- 

 duction can only take place when the limb has 

 been detached as high as the moveable base ; 

 for otherwise an hemorrhage supervenes which 

 kills the animal; 3d, that the reproduction 

 takes place only at the time of the moult, and 

 that the new leg is at hrst slender, but with all 

 its parts or joints, each of which increases pro- 

 gressively, until the whole has acquired its 

 natural relative size.* 



BIBLIOGRAPHY. Lister fy Way, Obs. concerning 

 the darting of spiders, Phil. Trans. 1669 and 1670. 

 Homberg, Sur les araignees, Mem. de Paris, 1707. 

 Clerck, Vom fangen und Ernahren der Spinnen Abh. 

 d. Schwed. Akad. J. 1761. Boissier de Sauvages 

 Ohs. sur une araigne, Mem. de Paris, 1758. Ha- 

 gedorn, Ue Araneis, Miscel. Acad. Nat. cur. Dec. 

 II. an 3, 1684. Valentini, Curiosa in araneis ob- 

 servata, ib. Dec. ii. an 7, 1688. Dorthes, Obs. on 

 the structure and oeconomy of some curious species 

 of aranea ; Trans, of Linn. Soc. vol. ii. Paullini, 

 De aranea rara, Misc. Ac. Nat. cur. Dec. iii. an 3, 

 1695. Garmann, Aranea aere nutriuntur ib. Dec. i. 

 an 1, 1670. Wurmb, Beschryving van te groote 

 tuin-spin van t'Eiland Java ; Verhand. v. h. Bataaf. 

 Genoot. Deel 3. Latreille, Sur la famille des 

 araignees mineuses, Soc. Philomathique, an 7. 

 Prevost, Sur les araignees mineuses : Mem. de la 

 Soc. d'Hist. Nat. de Paris, Cah. i. Martyn, Aranei ; 

 or, a natural history of spiders, 4to. Lond. 1793. 

 Hahn, Monographic der Spinnen, 4to. Nurnb. 

 1820-22. Ej. die Arachniden liv. 1 10. Clerck, 

 Aranei Suecici, 4to. Upsal. 1757. Muel'.er, Hydra- 

 rachos quas in aquis Daniae, &c. 4to. Lips. 1781. 

 Lister, Hist. Animal. Angliae, 4to. Lond. 1678; 

 Gerrnanice cum add. a Martini et Goeze, 8vo. 

 Quedlingb. 1778. Meyer, Ueber ein. Spinnen d. 

 Getting. Gegend. 8vo. Getting. 1790. Treviranus, 

 Ueber den innern Bau der Arachniden, 4to. Nurn- 

 berg, 1812. Heroldt, Exercit. de animal, verteb. 

 carent. formatione in Ovo Pars piitna : De genera- 

 lione aranearum, fol. Marb. 1824. Walckenaer, 

 Fa\ine Parisienne, 2 torn. 8vo. Paris, 1802; Ej. 

 Tableau des Araneides, 8vo. ib. 1805; Ej. Hist, 

 des Araneides, Fasc. 5, 12mo. ; Ej. et de Blainville, 

 c. Araneides de France. Lyonnet, Rech. sur 

 1'anatomie et les metamorphoses de differentes es- 

 peces d'insectes, 4to. Paris, 1832. Roesel, Insecten- 

 Bclustigungen, 4 torn. 4to. Niirnberg, 1746. 



(factor Audouin.) 



ARM. (Surgical anatomy.) (The arm, Gr. 

 Bftaftuv. Lat. Brachium. Fr. Bras. Germ. 

 Oberarm. Ital. Braccio.} The ancients ap- 

 plied this term to the whole of the upper 

 or thoracic extremity collectively, as most 

 persons do in ordinary discourse, at the 

 present day ; but .in anatomical language the 

 term is restricted to that section of the upper 

 limb included between the shoulder and the 

 elbow. The arm taken in this limited sense 

 is somewhat cylindrical, a little flattened, 

 however, on its internal and external surfaces, 

 particularly towards its middle ; it varies 



* Mr. Blackwall, in the paper already referred to, 

 has related an accidental discovery of the power of 

 some spiders to abstract respirahle air from water. 

 Several individuals have preserved an active state 

 of existence under water for six, fouiteen, or twenty- 

 eight days, spinning their lines and exercising their 

 functions as if in air, while others have not sur- 

 vived for a single hour. -ED. 



much in its proportions as to length and 

 volume : it is more rounded in fat persons, 

 and especially in females, in whom it assumes 

 more or less of a conoid form, tapering to- 

 wards its lower part. (See t /?g. 1 and 2, p. 3.) 

 The arm is composed of a single bone, the 

 humerus, several muscles, bloodvessels, ab- 

 sorbents, and nerves connected together by 

 cellular tissue, and inclosed in an aponeurosis, 

 which lies immediately beneath the common 

 integuments. Viewing the arm extended, the 

 hand being placed in a state of supination, 

 we observe at its superior and external part 

 a prominence of a triangular form, the base 

 of which is superior; this is formed by the 

 deltoid muscle, and is bounded before and 

 behind by two slight grooves, which unite 

 below in a depression called deltoid fossa, 

 situated immediately over the insertion of the 

 deltoid muscle; this deltoid fossa is the most 

 eligible part of the arm for the insertion of 

 issues, as it contains a considerable quantity 

 of cellular tissue, affording a favourable bed 

 for the reception of peas or other bodies in- 

 serted for the purpose of exciting suppuration, 

 while it possesses this additional advantage, 

 that no muscular fibres extend across it, whose 

 contractions might have the effect of deranging 

 the surface of the ulcer or the dressings neces- 

 sary to be applied to it, and thus causing an 

 unnecessary degree of pain. From the deltoid 

 fossa a superficial depression extends along the 

 outer edge of the arm, and terminates in the 

 triangular fossa in front of the bend of the 

 elbow: along the course of this depression 

 blisters are frequently applied by the Parisian 

 and other continental physicians in inflam- 

 matory affections of the thoracic viscera, 

 a mode of treatment not generally employed 

 in such cases by the physicians of this 

 country. Another depression extends along 

 the inner side of the arm from the axilla to 

 the hollow in front of the elbow, where it joins 

 the external depression. Between these two 

 depressions there is an oblong prominence an- 

 teriorly, formed by the biceps muscle, and a 

 more flattened prominence intervenes poste- 

 riorly, formed by the triceps which occupies the 

 whole of the posterior surface of the arm. 



Skin and subcutaneous tissue. The skin 

 covering the arm is soft and delicate; sebaceous 

 glands and hairs are not very evident on it, 

 especially in front ; it is thicker and stronger, 

 however, on the posterior surface. The basilic 

 vein is generally visible at the lower part of 

 the internal brachial depression, and the pul- 

 sations of the brachial artery may be felt along 

 the whole of its course : the cephalic vein is 

 sometimes visible, especially in thin persons, 

 along the course of the external brachial de- 

 pression. As the skin of the arm is loosely 

 connected to the subjacent parts, the edges of 

 simple incised wounds in this region are easily 

 retained in contact. The subcutaneous layer 

 of cellular tissue or superficial fascia contains 

 more or less adipose substance, in greater abun- 

 dance in women and children than in men, 

 and in greater quantity in the depressions than 

 over the muscular prominences ; the filaments 



