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cranium and the vertebral oohunn a free «egnientlialf is found, that 

 has certainly an osteogenetical, perhaps even a hemispondylogene- 

 tical potency. 



It is now the question whether this potency is activated, and if 

 so, what phenomena are the results of this activication. Though it 

 is not the intention of this communication to give a categorical 

 answer to the question submitted here, I will however indicate 

 already the direction in which, according to my opinion, the answer 

 must be looked for, and fix the attention to the fact that in the 

 cranio-vertebral region a great many phenomena present themselves, 

 the morpiiological signification of which has as yet not by far been 

 defined in the same way by all investigators. I have here especially 

 an eye to the variations of the atlas in the region of the sulcus 

 arteriae vertebralis, to the different phenomena on which in fact 

 tiie Fro-atlashypothesis of Aijjrecht is founded, to the concrescentia 

 atlanto-occipitalis and the manifestation of the occipital vertebra. 



I think, that all these phenomena can be brought under one 

 point of view, namely the existence of the above mentioned segment- 

 half la. 



A further investigation into this question will form the subject 

 of a following communication. 



Anatomy. — "27tó (/enetical signification of some atlas-variations ' . 

 By Dr. J. A. J. B.\rge. (Comnuinicated hy Prof. L. Bolk). 



In the previous communication, "On the metamerological signification 

 of the cranio-vertebral interval" I iiave fixed the attention to the 

 fact, verified also by investigation, that between the atlas and the 

 caudal boundary of the cranium, in consequence of the intersegmental 

 position of the craniovertebral interval and of the process of the 

 re-segmentation of the vertebral column, necessarily a free half- 

 segment must exist, indicated for the sake of brevity as the semi- 

 segment \a. 



At the end of this communication the question was raised, to what 

 phenomena the activation of the osteogenetic potency, doubtlessly 

 existing In this semi-segment, would give rise, and the provisional 

 answer to this question was, that, in my opinion, it would prol)ably 

 be possible to trace a relation between the established existence of 

 the semi-segment and a series of phenomena in the cranio-vertebral 



