. A system of anatomy for the use of students of medicine (Volume 1). vers; but the colour of this portion of the cutis dependsupon the state of the circulation; and becomes livid when theblood is disoxygenated, or when the circulation ceases there;and this colour also appears through the nails. The nails are unquestionably organised, although their ulti-mate structure is not known. They appear to be composed oflamellae, and these lamellae of fibres. They grow rapidly, andwrhen they are not pared or worn away, they sometimes acquirean immense size. As a remarkable instance of this, it is relat
. A system of anatomy for the use of students of medicine (Volume 1). vers; but the colour of this portion of the cutis dependsupon the state of the circulation; and becomes livid when theblood is disoxygenated, or when the circulation ceases there;and this colour also appears through the nails. The nails are unquestionably organised, although their ulti-mate structure is not known. They appear to be composed oflamellae, and these lamellae of fibres. They grow rapidly, andwrhen they are not pared or worn away, they sometimes acquirean immense size. As a remarkable instance of this, it is related, that a nail ofthe great toe was sent from Turin to the Academy of Sciencesat Paris, which measured four inches and a half in length. The growth seems to take place altogether at the roots. The nails, when chemically examined, appear to consist of amodification of albumen; and thus resemble cuticle and horn intheir composition. —The growth of the nails, forwards, is entirely from a foldof the cutis vera, at its root, called, though not with exact pro- Fig. prietv, the matrix of the nail, as seenin Fig. 32. It grows also in thicknessfrom the upper surface of the skin,upon which the nail rests. In theformation of a new nail the lamenwhich starts from the matrix, receivessuccessive layers, as it approaches theextremity, the deepest seated of which is the shortest. In thisway the nail gets its thickness and strength, and occasionally,where the deposition of new matter, goes on more rapidly underthe body of the nail than at the matrix, the body is thrown up intounsightly rugosities. Its developement is exactly similar to thatof the horns and hoofs of animals. The striated appearances ofthe nail, is said to be owing to the papillary prominences white semicircular line at the root, is called the lunula.—The nails are not exactly analogous in structure to the cuticle,in the ordinary acceptation of the term, to that part which israised up under a blister. The prope
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