252 BIOLOGICAL PHYSICS 



Likewise, in the development of the nascent vertebral 

 column, the foundation plan, and materials, have been 

 determined upon, and laid down, by the evolving sym- 

 pathetic nervature, antecedent to the appearance of the 

 nascent systemic nervature, which, when it has attained 

 the requisite degree of development, diverts the necessary 

 materio-dynamic elements into the notochordal texture, 

 to accomplish the ossification of the bodies of the future 

 vertebrae, and to ensure a stable foundation being con- 

 structed for the fully developed systemic nervature. On 

 both these procedures follows, the removal, or involution, 

 of the no longer required, reparative, or constructive, 

 materials, as residual elements, as should always follow on 

 the lapse of function, in order to leave no nidus, or 

 nucleus, on which the agencies of disease can seize, and 

 convert, to pathogenic uses, therefore, absorption ensues, 

 in the one, and shrinkage, in the other, until, physio- 

 logically, their presence is known no more. 



Along with the physiological working out of these 

 problems, unfortunately, pathological presences may "turn 

 up " on the scene, such as rheumatism et hoc genus omne, 

 when, what has been a process of " plain sailing," becomes 

 one of " tacking, and turning," until the vis medicatrix 

 nature succeeds in thwarting the intentions of the enemy, 

 and restoring order. 



In regard to the very early appearance, in the embryonic 

 structural economy, of the notochord, as a definitely 

 organised element, and its subsequent all but complete 

 disappearance, we are persuaded, more and more, that it 

 subserves one of the most important, formative, or 

 developmental, purposes ; more especially, as we have 

 said, in connection with the process of ossification, and 

 the formation of that part of the skeleton, which is 

 destined to, continue, and protect the central structures 

 of the systemic nervous system ; thus, up to the time of 

 its appearance, no indication of the skeletal tissue has 

 manifested itself, and nothing, but the most rudimentary 

 indication, of neuro-muscular development, which, 

 according to our views of the nutritional functions of the 

 notochord, precludes the possibility of ossification taking 

 place from it, at that formative juncture ; what more 



