203 



first cervical nerve, and in this way a .short channel or ring-sha|)ed 

 opening is formed. To indicate this opening Bolk uses the name of 

 foramen atlantoideiim laterale, whilst Gaupp proposes to borrow the 

 denomination that the veterinary surgeons (Ellknberger and Baum) 

 give to its homologon, constantly occurring with many animals, the 

 foramen alare. The osseous bridge that shuts off this foramen at 

 the top I call ponticulus lateralis. 



As I remarked already previously both variations are known in 

 literature. Le Double ') indicates the frequency of the foramen 

 allant. posterior and the ponticidus lateralis as 11. 7% that of the 

 foramen atlantoideum and the ponticulus lateralis as 1.87o- 



In the collection of atlases of the Anatomical Laboratory in 

 Amsterdam, I found among 3360 atlases 77 or 2.3% with foramen 

 atlantoideum laterale and 355 or 10.67„ with foramen atlantoideum 

 |)os(ei'ius. The numbers resulting from the examination of this material, 

 which is at least twice as huge as the complete collective tables from 

 which Le Double calculated his percentage do consequently not 

 considerably deviate from the latter. 



The simultaneous occurrence of these two variations at the same 

 atlas has a.o. been described by Bolk '), who found a combination of 

 a foramen atlantoideum laterale and a bilateral foramen atlantoideum 

 posterius on the right side. 



Le Double (l.c.s.) mentions likewise a case in which on the right 

 side the two foramina with the ponticuli belonging to them were 

 simultaneously present. 



From the material that was at my disposal, I could select a 

 series, in which all imaginable coincidences occur, as appears from 

 the following summary : 



1. For. atl. lat. bilateral For. all. y. 



2. „ „ „ „ „ „ 



3. „ „ „ 



4. „ „ „ to the left „ „ 



5. „ „ „ „ „ „ „ 



6. „ „ „ „ „ „ „ „ 



7. „ „ „ „ „ right „ 



8. „ „ „ „ „ ,, ,. „ 



9. „ „ „ „ ., ,. „ „ 



10. ,, ,, ,, missuig ,, ,, 



11. „ ., „ „ ,. „ 



12. „ „ „ „ ., „ 



') Le Double. Les variations cle la colonne vcrlébrale. 



-1 L. Bolk. Do variaties in hel grensgebied tusschcu hoofd en halswervel- 



