246 



BIOLOGICAL PHYSICS 



suppose that the materials entrusted to the notochord 

 for nutritive disposal, consist of, amongst others, the 

 inorganic, or more mineral, elements of bone structure, 

 which it deposits, for metabolic purposes, in the sym- 

 pathetically constructed fibre-cellular foundation elements, 

 or centres of ossification, of the future individual vertebrae, 

 as well as, for the growth, and development, of all the 

 continuous textural extensions and terminal distributions 

 associated therewith, or proceeding therefrom. 



FIG. 105. DIAGRAM TO SHOW THE POSITION OF THE ENLARGEMENTS OF 

 THE NOTOCHORD IN PASSING THROUGH THE VERTEBRAL COLUMN. 

 Half the natural size. (After KSlliker, A. T.) 



ch, notochord ; b, bodies of two vertebrae ; iv, intervertebral plate with the wide 

 enlargement of the notochord ; bn, ossific nucleus of the bodies of the vertebrae ; 

 e, slight dilatations of the notochord opposite the epiphysial plates. 



The reason of the structure in question lapsing at 

 this stage of organic evolution is, that it ceases to occupy 

 the position of an active, vehicular, or vascular, structure, 

 and, like such unemployed ducts as the thyro-glossal, 

 fails to attract further notice. During the period of 

 its functional activity, or before the nutrition of bone, 

 generally, is effected by periosteal agency, we have the 

 materials, for the growth of bone, carried to the bodies 

 of the future vertebras by notochordal means, and their 

 ossification in advance secured, in preparation for the laying 



