We have successively observed a great num ber of individuals of this species which were mutilated of one or more legs. It was not without surprize that the author of this article observed the first spider that was experimented upon, and which wanted a leg, change its skin, and after that operation reappear with eight legs. The like occurrence was frequently ob served ; the new leg was two or three lines in length when it first appeared, that of the oppo site side being less than an inch : each of the joints of the former continued to grow during the whole of the year.
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 first slender, but with all its parts or joints, each of which increases pro gressively, until the whole has acquired its natural relative size.* ARM. (Surgical anatomy.) (The arm, Gr. Bqctvwv. Lat. Brachium. Fr. Bras. Germ. Oberarni. 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 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 colloid form, tapering wards its lower part. 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 of the cutaneous nerves of the arm and the superficial veins and absorbents lie imbedded in it : thus the cephalic vein and twigs of the external cutaneous nerve appear along the outer edge of the arm, and along the inner edge are found the internal cutaneous nerve, the brachial branches of the second and third intercostal nerves, the cutaneous nerve which arises from the ulnar high in the axilla, the basilic vein, and a few lymphatic glands, which lie at from one to three inches above the internal condyle.