

VEINS 231 



The external jugular is a secondary channel formed by the union of a superficial 

 facial vein and a vein in the neighbourhood of the ear. It extends backwards 

 and unites with the primitive or internal jugular, near its junction, with the 

 subdavian vein from the arm. 



FIG. 288. DIAGRAM OP THE VEINS OP THE HEAD AT THE BEGINNING OP THE THIBD MONTH. 

 (After Mall.) Lettering as in fig. 287. 



A secondary anastomosing vein is formed between the external jugular and the lateral sinus, 

 which emerges through a foramen in the temporal bone (foramen jugulare spurium). This 

 occasionally persists in the human adult, and in certain mammals it enlarges and, owing to the 

 disappearance of the primitive jugular, draws all the blood from the cranial sinuses. Salzer 



FIG. 289. DIAGRAM OF THE VEINS OF THE BRAIN OF AN OLDER FCETUS. (After Mall.) 



Lat.Sin., lateral sinus (v. cerebralis posterior) ; Sup.Pet., superior petrosal sinus (v. cerebralia 

 media) ; SS, Sylvian or middle cerebral vein ; SPS, sphenoparietal sinus ; SB, sinus rectus ; 

 ILS, inferior longitudinal sinus ; VG, vena galena magna. Other letters as in fig. 287. 



(1895) first showed that the view of Luschka, according to which this channel ^represents the 

 primitive jugular, is untenable ; and Mall, whose account has been here followed, has recently 

 confirmed Salzer's descriptions in the case of the human embryo. 1 



1 Salzer, Morph. Jahrb. xiii. ; Mall, Amer. Jour, of Anat. iv. 1905. 



