207 



In order to examine in how far the possibilitj' expressed here is 

 likewise a reality, we ought in the first place to remember what has 

 been said in the previous communication on the metamerological 

 signification of the cranio-vertebral iiiterval about the metamere 

 relation of the vertebrae. 



From the generally admitted and in fact ascertained law of the 

 re-segmentation of the vertebral column we have then deduced that 

 in general the n"' vertebra has been constructed from ihe caudal 

 half of the ?*'•' scleromere and the cranial half of the C»-)-!)''' 

 scleromere, so that the metamere formula of the vertebrae is 



Vl^ertebra) n = Snb + S (/« + J ) U. 



If now we admit that the atlas, with regard to its metamere 

 relations, is entirely equivalent to Ihe other vertebrae and that 

 consequently the above-mentioned formula likewise holds good 

 for the atlas, then follows from it necessarily (supposing n=z\), 

 that the atlas would be constructed from the caudal iialf of Ihe 

 first segment and the cranial half of the second one. 



Lei us now regard in this connection the position of the ponticuli 

 posteriores and laterales. 



civ 



■■V.c.m 



Fig. 2. 



Gh — chorda m = myotome; AB = cranio-vertebral interval; 



S I = 1st Segment; S It = 2d Segment, etc. a = cranial 



serai-segment; b = caudal semi-segment; n. c. 1 = le cer- 



vicalnerve; v. c. 11 = axis. 



To the nature of the ponticuli belongs that they form Ihe cranial 

 extremity resp. of Ihe foramen arcuale and of the foramen alare, 

 through which foramina the tiret cervical nerve passes. Both the 

 ponticuli are consequently always situated cranially from this first 

 cervical-nerve. Fig. 2 however teaches us, according to the law, 



