Ml 



SKELETON. 



8KIN. 



part of the Leg. It* upper put, or Head (1), U far larger than any 

 other. IU upper lurfaoe ii nearly oral, it* greatest diameter being 

 tnnavene ; and it preaent* two slightly concave oval smooth surface* 

 (S, S), on which the condyles of the femur rest. Between them i* an 

 eminence, named the Spine, which fit* in between the eondyles, and 

 to which, a* well as to rough surfaces before and behind it, the crucial 

 ligaments and aemilunar cartilages are fixed. Below and on the sides 

 of the bead are tuberocities, on which the lateral ligament* are 

 inserted, and behind the external tuberoaity is a smooth surface which 

 articulate* with the head of the fibula. In front, and a little below 

 them, i* the tubercle (4) to which the ligamentum patella is attached. 

 Below this the body (5, 6) is triangular, and as it descends, becomes 

 smaller ; its outer surface is hollowed ; it* inner, which forms the 

 akin, slightly convex ; it* posterior rounded. The outer border gives 

 attachment to an interoaaeous ligament, which fills up the space 

 between it and the opposed part of the fibula : the anterior is sharp 

 and prominent, and is named the Crest. The lower or tanal extremity 

 U a little expanded, and has a somewhat quadrilateral form. It* 

 outer aspect has a slightly concave surface, which is articulated im- 

 moveably with the fibula ; the inner is prolonged into a bluntly 

 pointed process, the internal malleoln* (6), which has the internal 

 lateral ligament of the ancle fixed to its extremity, and a smooth 

 surface on it* outer side, which articulates with the astragalus. The 

 anterior surface of this extremity ia smooth where tendons pass over 

 it ; the posterior is flat ; the lower or terminal surface (7) is quadri- 

 lateral and slightly hollowed ; it rests on and U articulated with the 

 astragalus. 



The Fibula (Jig. 24, B) is situated at the outer part of the leg, and 

 is fixed immoveably by the side of the tibia. It is long, very slender, 

 for the most part three-sided, and iolarged at either extremity. The 

 upper extremity or head (1) is the smaller; it is rounded, and on its 

 upper and inner part has an oval smooth surface, with which it arti- 

 culates with the outer tubercle of the tibia ; the rest of its surface 

 is uneven, for the attachment of ligaments and a tendon. The lower 

 extremity (2) is longer and more pointed than the upper ; it forms 

 the external malleolus, or outer ancle, to whoso extremity the exter- 

 nal lateral ligament of the joint is attached, and whose inner surface 

 is articulated with the astragalus ; behind it is a deep groove, over 

 which the tendons of some muscles of the leg pass to the sole of the 

 foot. Above the malleolus, and on the inner aspect of the fibula, is a 

 smooth surface, where it is united with the tibia. 



The Patella, or Knee-Pan, has a somewhat triangular outline. Its 

 narrowest part is below, and is fixed by the ligamentum patella; to 

 the tubercle of the tibia. Its anterior surface is slightly convex, and 

 looks fibrous, being marked by the insertions of the tendons of the 

 extensor muscles of the leg ; the posterior is smooth, and divided by 

 a ridge into two parts, of which the outer i* the larger, and which 

 are adapted to the pulley-like surface between the condyles of the 

 femur. 



The Tarsus is composed of seven bones, namely, the Astragalus 

 (1), Os Calcis (2), Navicular (3), Cuboid (4), Internal (5), Middle (6), 

 and External (7) Cuneiform Bones. These are set together so that 

 they cannot be moved by any slight force, and yet are possessed of 

 considerable elasticity. The Astragalus is that on which, through 

 the Tibia, which rest* upon it* upper quadrilateral surface, the weight 

 of the body first falls. With the Tibia above, and the two malleoli 

 on either side of it, it forms the ancle-joint, a hinge with a limited 

 lateral motion. It* lower part rest*, with two surfaces of contact, on 

 the os calcia, whose hinder prominent part (8) forms the heel ; and 

 it* anterior portion, or head, is received in a cavity, formed by the 

 navicular bone in front, part of the os calcia behind, and a very strong 

 ligament below and between them. This cavity is at the summit of 

 an arch which the tarsus and metatarsus together contribute to form, 

 and of which the support* are the os calcia behind and the ends of 

 the metatarsal bones before. It is indeed a double arch, for it has at 

 the sole a concavity, both from before backwards and from side to 

 aide; and the strength with which its several part* are joined is so 

 great, that few accidents are rarer than a fracture or dislocation of 

 any of the bones of the tarsus. 



The rest of the bones of the Foot, including those of the Meta- 

 tarsus (9, 9) and the Toe*, are in number, arrangement, and form very 

 imilar to the Metacarpus and the Phalanges of the Fingers. The 

 metatersal bones however are longer, more slender, and set more 

 cloorly side by side than the metacarpal ; and the Phalanges are all 

 much shorter, and (except the two of the great Toe) smaller. Their 

 movement* are in general the same a* those of the fingers, but leas 

 exteiwive ; neither is there any adaptation for so free a movement of 

 the first toe a* of the thumb. 



There are some supplemental bones of the skeleton, which need 

 but jiut be mentioned. These are the Sesamoid and the Hyoid Bones. 

 The former occur within the substance or in the course of tendona 

 which are much exerted ; the patella i* the largest of them ; the 

 number and existence of the others are not certain, but there are 

 almost always two at the first joints of each of the thumbs and great 

 toe* ; they are small, oval, or round, and rough on all their surface*, 

 except that by which they articulate with the bone on which they lie. 

 The Hyoid Bone is that on which the larynx is suspended, and the 

 baa* of the tongue fixed ; it is not articulated, except by long liga- 



ments, with any other of the bones, f LARTNX ; TOKODE.] In rela- 

 tion to many point* in this article, the following articles may be 

 consulted: ARTICULATION, BO.XK, VERTEBRA, LOCOMOTION is AMI- 

 HALS, MAX. 



SKENEA, a genus of Qasteropodous Mollu$ca, named after Dr. 

 Skene. The shell U very small, flat, and with few whorls. It is 

 deeply umbilicated ; the mouth is entire, circular, not quite connected 

 with the body whorl ; operculum rather spiral. The animal is nearly 

 like that of Rittoa, and has large eyes. The species are few, and are 

 found generally on the root* of CoraUina orHcinalit. 



SKIMMER. [RTSCHors.] 



SKIN. The Skin, or Derma, is the outer covering of the body ; 

 and having to serve at once aa a defence for the more deeply seated 

 structures, aa an organ of touch, and as an apparatus for secretion, it 

 is one of the most compound of all the tissue*. 



It ia composed of two chief parts : a vascular basis named Cutia, 

 and a superficial layer named Epidermis, or Cuticle, which ia not 

 vascular. The cutis is made up for the most part of fibres and 

 lamina;, like those of common cellular tissue. They are much more 

 densely woven near the surface than in the deeper part of the skin : 

 in the former they constitute a very tough and elastic compact mem- 

 brane ; in the latter they are arranged in irregular large cell*, which 

 in moderately stout persons are filled with fat, but in the emaciated 

 are collapsed, and form a loose flocculent white tissue. This general 

 form of structure prevails through the whole akin ; but in different 

 parts of the body, and still more in different persons, the density snd 

 thickness of its layers, the size of the cells, the quantity of fat which 

 they contain in the deeper parts, and the fineness or coarseness of the 

 tissue composing them, vary considerably. 



The external surface of the skin presents a variety of wrinkles. 

 The larger of these are produced by the action of muscles, which ia 

 many part* throw the skin into folds ; others result from its loss of 

 elasticity in old age, and the removal of the fat beneath it ; and again 

 others, which are seen most plainly on the palms and the balls of the 

 fingers, and on the corresponding parts of the foot, run in very close 

 parallel arches, and indicate the arrangement of subjacent rows of 

 sensitive papilla!, with which the whole surface of the skin is beset, 

 and which in the parts just named, and in some others, are arranged 

 in regular double lines. In their most developed state, on the balls 

 of the fingers for example, the papilla; are very fine conical processes, 

 standing somewhat obliquely, and so densely set, that their summits 

 form a seemingly smooth surface. On these part* each elevated line 

 which one sees on the surface has beneath it two rows of papilla) ; 

 for when looked at closely, each such ridge shows on its summit a 

 little furrow dotted with minute apertures, and which fita into the 

 space between the rows of papilla;. Over the rest of the body the 

 papilla; are much smaller, and are irregularly arranged. Everywhere, 

 however, they are the most vascular part of the skin, each papilla 

 receiving a distinct loop from the subjacent network of bloodvessels. 

 It is in them also that the greater part of the very numerous nerves 

 of the ekin terminate ; for though every part of the skin be sensitive, 

 yet the papilla; are so in the highest degree, and are the chief instru- 

 ments by which the sense of touch is exercised. [SENSKS; NEUVOI-S 

 SYSTEM.] It is through their being so much developed, that the tips 

 of the fingers are adapted for the perception of the finest impressions 

 of the sense ; though even they have less delicate perception than the 

 tip of the tongue, on which similar but larger and more pointed 

 papilla; are set. 



The chief secretory apparatus of the skin consists of the perspira- 

 tory glands, which are disposed over its whole extent, but, like the 

 papillae, are largest and moat numerous in the palms and soles. By 

 looking on the surface of the cuticle covering these parts, one may 

 see, especially on a warm day, or when perspiring freely, a number of 

 minute orifices between and upon the tops of the arched ridges already 

 described. These are the orifices of the glands by which the per- 

 spiration is secreted, and sometimes one may squeeze through them a 

 drop of the clear crystal fluid which the glands produce. Each orifice 

 leads to a fine tube of somewhat lees diameter than itself, which 

 passes down through the epidermis, and into the deeper parts of the 

 skin, making on its way several spiral turn', and ending in a slightly 

 enlarged closed sac. In the sole, each such tube makes from 15 to 20 

 spiral turns ; in the palm, from 6 to 10 ; in other parts, fewer : in the 

 right hand the spiral turns are made from left to right ; in the left, 

 from right to left There are about 25 of these orifices in a nquaru 

 line of the surface of the tip of the fore-finger; and about 75 in the 

 same space between the 1-ases of the fingers : taking therefore the 

 whole superficies of the body at 14 square feet, it in probable that, 

 as Kichhorn calculated, there are not less than ten millions of the e 

 glands scattered through the skin. 



It is in them that the perspiration is being constantly formed, 

 though it most generally passes away as fast as it is produced in an 

 invisible vapour, and during health collects in the form of sweat only 

 when it is very rapidly formed, as during active exercise, or when the 

 surrounding atmosphere is already saturated with moisture. Tlia 

 fluid of the penipiration is composed of water, with very small quanti- 

 ties of animal and saline matter, some free lactic acid, nitrogen, aud 

 carbonic acid. By thus removing carbonic acid from the blood, the 

 akin is, next to the lungs, the most important and essential excretory 



