ON THE NOTOCHORD 



253 



essential then than that a temporary developmental pro- 

 cedure, or expedient, should take place, and a temporary 

 organism be provided, to meet the temporary organic 

 occasion ? And this is, neither more nor less, than what 

 takes place under the circumstances, by the evolution of 

 the structure known as the notochord. In this temporary 

 developmental procedure, we, therefore, claim, that a great 

 materio-dynamic problem has been carried out, by which 

 formative difficulties, otherwise insurmountable, have been 

 overcome, and the first step forward been taken, in the 

 production of a vertebrate and skeletally possessed, 

 animal. 



In the provision made for the purpose, we see a tem- 

 porary ductiform structure laid down from the anterior 

 end of the neural canal, from which we conclude is 

 drained off, from the contents of that canal, the earthy 

 salts, necessary for effecting the ossification of the future 

 vertebral bodies, the percolation of them into the fibro- 

 cellular matrix of these bodies, and the subsequent carti- 

 laginous consolidation, and ossification, of them, followed 

 by involution, and very slight survival of the temporary 

 structure. 



After the development of the neuro-musculature, the 

 process of ossification, and skeletal nutrition, are effected 

 through the joint agency, of nerve, muscle, and inter- 

 mediate, or uniting musculo-skeletal, textures, tendonous, 

 and periosteal. 



Lime, among other earthy ingredients of living proto- 

 plasm, becomes, thus, separated from its physiological 

 companionship with the other plasmic elements, and is 

 transmitted, by means of notochordal circulation, to effect 

 a new mode of union with these elements, by being, as it 

 were, strown amongst them, to give them the property of 

 solidity, and the consequent power of resistance, and 

 adaptability to the structural necessities of the growing 

 organism, in its evolution of an articulate skeleton 

 lime, thus, once more asserting itself, as one of the most 

 essential elements in nature, as well as one of the most 

 widely distributed. 



It is, thus, most remarkable, that earthy matter is 

 separated from the sympathetically innervated organic 



