272 Likenesses ; or, Philosophical Anatomy 



study and contemplation — one such mode being the study of 

 the development of such organism. But a synthesis of all 

 our modes of study is the necessary preliminary to our 

 obtaining the least imperfect apprehension which is possible 

 for us of any animal or plant. We cannot grasp it in its 

 totality and unity — in its essence — we can only comprehend 

 it approximatively, as we approach it, intellectually, on as 

 many different sides as we can, and as nearly as we can. 



To return to the question of the vertebral or non- vertebral 

 nature of the skull : the result of all the controversy on the 

 subject, up to the present time, is that such vertebral nature 

 may be affirmed in one sense and denied in another, accord- 

 inof to the line of thought Avhich is followed. 



The whole body of every animal with a distinct skull and 

 backbone exists at first as a rounded, almost structureless, 

 mass of tissue, in which the first clear indication of such 

 animal is a longitudinal furrow marking the place of the 

 future spinal marrow and brain. Beneath this furroAv a rod 

 made up of cells (the chorda dorsalis) comes to lay the 

 foundation of the future spinal column. From each side of 

 the groove a fold extends upwards, the two folds being called 

 the lamince dor sales, and these folds meeting together above, 

 form a canal. It is within that part of the lamince dorsales 

 which form the spine that first the cartilages, then the bones, 

 are developed which form the sides of the vertebral arches. 

 Similarly, it is within that part of the laminw dorsales which 

 form the skull that first the cartilages and then the bones are 

 developed which form the sides of the skull arches, and thus 

 there is an undeniable similarity between these two parts. 

 Moreover, in subsequent development, the bones of the skull 

 — especially in the higher animals — present a singular 

 reminiscence of vertebrae in the three serially successive 

 arches which they form. Certainly, if the essence of vertebrae 

 consists in their being a series of bony rings fitted together, 



