304 THE SOLIDS. 



experiments really seem to prove is, that bones in contact with 

 blood-vessels containing the colouring matter of madder readily 

 imbibe and retain that principle in common with the liquor 

 sanguinis. 



The bones of old animals are coloured with much more 

 difficulty than those of young ; a few hours in very young 

 animals being sufficient to ensure their colouration. 



Development of Bone. We come now to consider the 

 exact process of the development of bone. 



Bone is developed either in membrane or in cartilage ; 

 when in the former it may be termed intra-membranous, and 

 when in the latter mtra-cartilagmous ossification. 



Infra-membranous Form of Ossification. We will con- 

 sider, first, the intra-membranous form of ossification. Dr. 

 Nesbitt * was the first to distinguish between the two types 

 of ossification. More recently Dr. Sharpey f has described 

 clearly and satisfactorily the steps of the intra-membran- 

 ous development. This form he considers to belong to 

 certain flat bones of the cranium, as the parietal and por- 

 tions of the frontal and occipital bones, as well as to the 

 outer surfaces of the long bones. 



The first perceptible ossification of the parietal bone, 

 which may be selected as one of the best examples of this 

 form of osseous development, consists of a network of 

 spiculae of bone, the outermost of which radiate in lines to- 

 wards the circumference, and are connected by short trans- 

 verse branches. (See Plate XXXIII. figs. 1, 2.) 



As the ossification proceeds, the first-formed spiculse, in 

 the centre of the bone, become greatly increased in thickness, 

 and the spaces between them much diminished in size ; the 

 ossification continues thus to spread and consolidate until the 

 parietal meets the neighbouring bone, with which it is at 

 length united by suture. 



If, however, the microscope be brought to bear upon one of 

 the newly-formed spiculae before the entire bone has attained 



* Human Osteogony, Lond. 1736. 



t Dr. Quain's Anatomy, edited by Mr. Quain and Dr. Sharpey, 5th 

 edition. 



