INTRODUCTORY REMARKS. 3 



i 



I hope to be able, by keeping strictly to the description of what I have seen, by describing 

 the structures in an ascending manner i. e. from the lower vertebrate type to the higher by 

 treating histology for the time as a handmaid and not as an equal, and by keeping clear of all 

 mention, even, of the use of the parts, to transplant the roots of my ideas into the mind of my 

 readers. 1 If I can thus show the relation of the parts to each other, their varied modifications 

 in the ascending series, and the place they occupy correlatively to the skeletons of which they form 

 a part, I shall have done a real service to science ; for if this slow painstaking method of com- 

 paring form with form result in the discovery of the real nature of the parts, it will lead to more 

 and better work from younger hands and fresher minds. 



It will be better, it seems to me, to give the results of my own work than to keep 

 " rounding about " amongst the theories that have been already propounded : so that it will be 

 my work to say where I have found the scapula, for example, and not to say who called it a 

 " pleurapophysis," or who put it amongst the sternal ribs and called it a " hsemapophysis." 



Before entering upon special description it will be well to say a few words on the skeleton 

 generally. 



The vertebrate animal has its framework developed from several sources : firstly, from sym- 

 metrical cartilages which appear at first on each side of, and in close proximity to, the absolutely 

 azygous notochord these are developed upwards over the spinal cord, and downwards over the 

 viscera ; and in the head they are developed forwards to form the greater part of the skull and 

 much of the face : this is the axial skeleton. 



Secondly, many cartilages are formed between the axial skeleton and the skin; these are 



A . The labial cartilages ; 

 B. The sense-capsules ; and 

 c. The fins or limbs. 



The latter may lie in the vertical line, as the roots of the vertical fins of Fishes ; or on the 

 sides of the body outside the vertebral arches, as the lateral fins or limbs proper. 



The Sternum is nothing else than the lower part of certain of the costal arches a part in 

 which the segmentation, which is so perfect in the region of the notochord, dies out more or less, 

 and only perfectly revives afterwards in the growing young of the highest vertebrate types. 



The Shoulder-girdle, like the Hip-girdle, is composed of two halves, each of which is the root 

 KnA foundation of the limb of the corresponding side, and it is subject to the same law of vertical 

 and transverse fission as the limb itself, which is merely its divergent and freer continuation. 



Altogether, the cartilaginous skeleton may be called the endo-skeleton ; and its division be 

 into axial and accessory. The limbs, both root and branch, belong to the latter category. 



There is also, ancillary to the cartilaginous, a fibrous skeleton, of almost equal importance, 

 in some cases, to that which is formed of true hyaline cartilage. 



This is the skeleton of the skin and its infoldings, the exo-skeleton ; and prior to ossifica- 

 tion it is entirely composed of fibrous connective tissue in a more or less developed state. 



1 " For it is in knowledges as it is in plants : if you mean to use the plant, it is no matter for 

 the roots ; but if you mean to remove it to grow, then it is more assured to rest upon roots than slips : 

 so the delivery of knowledge, as it is now used, is of fair bodies of trees without the roots good for 

 the carpenter, but not for the planter. But if you will have sciences grow, it is less matter for the 

 shaft or body of the tree, so you look well to the taking up of the roots." BACON. 



