1. Deficiency And Excess Of Development

The entire bony fabric of the body has been found wanting in some few cases of monstrosity, and even in some individuals whose development in other respects was quite natural. A partial deficiency of the skeleton is less unfrequently observed, as it occurs in various parts of the body where development generally has been arrested; in the thorax, for instance, and the pelvis, and especially in the limbs. There is very commonly no bone in supernumerary peripheral parts, whether fingers, toes, or limbs.

Moreover, the skeleton very often falls short of its complete development, in being altogether cartilaginous, or at least very imperfectly ossified, at the time of birth. This condition, known as congenital rickets, sometimes continues to a later period of life, and betrays itself by insufficient firmness and power of resistance in the bones, by persistence of those characters which belong to the skeleton in childhood, by the apophyses remaining separate, etc. It is very commonly combined with hypertrophy of the white substance of the brain. In some cases the complete formation of the bones is retarded by long-continued and exhausting diseases, and in some parts of the skeleton it is very frequently arrested, to a great extent, by pressure from within; as, for instance, in the skull.

An excess of development is exhibited, on the one hand, when the whole skeleton, or parts of it, are completely formed at an unnaturally early period; as when the fontanelles close, the sutures disappear, the epiphyses unite with the diaphyses, the teeth are cut, etc, prematurely; and, on the other hand, it is seen, also, when the bones are unnaturally dense and hard, when they grow out and enlarge in some unusual direction, or when various new bony formations are found upon them.

The bones may vary in number either way; they may be more numerous or fewer than natural. When certain parts are wanting, or exceed their natural number, the corresponding bones are wanting or supernumerary too: but this may be the case also when a part appears to be naturally formed, as we find exemplified in the toes and sesamoid bones, in the vertebrae, and the ribs. The most frequent instance in which the number of the bones is usually great (although it is only an apparent excess), is when the pieces of which a bone is composed continue separate, or when, in the skull more particularly, unusual sutures, or sutural (Wormian) bones exist. The want of a bone is sometimes made up for by a supplementary increase in the bulk of a neighboring bone.