It is far more important to know that ten vertebrae are concerned in the formation of the pelvis and coccyx, than that this Anatomist counted 260, and that one 197 bones in the entire skeleton. It is not the less necessary to recognise the stunted abdominal ribs, than their long and movable representatives in the thorax. The number of vertebrae of which a vertebrate animal is composed may be easily ascertained. In man there are 37 or 38, namely :—
4 or 5 coccygeal, 5 sacral, 5 lumbar, 12 dorsal, 7 cervical, 4 cranial, 37 or 38.
By referring the segments to one common type, we may ascertain the number of elements of which each is composed, and then, by adding the aggregate amount of bones which form the four extremities, we shall make some approach to a correct estimate of the whole. But difficulties beset us in the outset. The typical number of the carpal bones is ten, and not eight. The os scaphoides and the os unciforme are each composed of two distinct bones. The os calcis in the tarsus represents the os cuneiforme and os pisiforme. In the enumeration of the bones how are we to count these compound pieces ?
In this calculation, however, other bones are omitted altogether, being unconnected either with vertebrae or with their appendages. Such are the turbinate bones, the cornua sphenoidalia, the ethmoidal cells, the primitively distinct petrosal bones, the lacrymal bones, etc. Of these, some receive the terminal filaments of the nerves of special sense; others are connected with the common covering of the body, and belong to the dermal skeleton. The thyroid cartilage and the rings of the trachea have an equal right with the os hyoides to be included in the present survey, under the division of the splanchnic skeleton; for the deposit of the amorphous and granular phosphate of lime in a cartilaginous and organized matrix is not a step towards perfect development, but is rather an adaptation of the ingredients to special purposes. The elastic cartilaginous skeleton of the shark is quite as highly organized and as complete as is the osseous skeleton of man.
Until the archetype, then, has been determined, it is useless to attempt accurately to ascertain either the number of the parts which should be included in the skeleton, or the nature of the elements of which each part is composed.
The want of accuracy in the application of names has led to many evils. It has deterred the student from extending his observations beyond the narrow sphere of human anatomy; for how could he, whose memory was oppressed by the dry details contained in a dissecting manual, hope, with advantage, to commence the study of the structure of other animals, whose component parts had been described from other quarters, or in other countries, under names which had no resemblance to those with which he was familiar ? And yet the two masterspirits of their day, John Hunter and Cuvier, saw well, and taught that a correct knowledge of the human frame could be gained only by comparing the organism of man with that of the other created beings by which he is surrounded. They differed in the course which they pursued in one respect, namely, that whilst Cuvier commenced with man as the most perfect animal, and descended thence step by step to those less highly organized, John Hunter started from the simplest forms, and traced the gradual adaptation or development of parts to meet the exigences to which an animal in its higher vocation was exposed.