§ -3 BLOOD SUPPLY OF HYPOPHYSIS 63 



reminding one strongly of the glomus caroticus (h) , for 

 from this bloodvessels numerous arterioles arise which wind 

 themselves over the entire artery, and, after a short course, 

 are taken up in a vein (m). Some of these arterioles break, 

 as arteriae nutriciae hypophyseos through this connective 

 tissue septum, penetrating into the lobus tuberalis (g). As a 

 second source of arterial blood supply there are bloodvessels 

 which originate in the arteria cephalica (k), and are situated 

 at the front of the thalamus opticus, running through the 

 stalk into the hypophysis. These are the arteriae infundi- 

 bularis superficiales and internae. Immediately before 

 entering the stalk of the hypophysis the superficial artery 

 suddenly divides into a ball of capillaries, which shortly after 

 are gathered again into a few arterioles, running through the 

 stalk towards the lobus posterior. This artery, therefore, 

 which lies in the dura, but remains close to the surface of the 

 thalamus, constitutes a kind of vascular network, whose 

 significance has not thus far been elucidated, but from whose 

 position, immediately in front of the hypophysial stalk, 

 we may conclude that it bears some relation to the hypo- 

 physis. From the caudal part of the thalamus, also an artery, 

 the arteria infundibularis posterior descends through the 

 stalk at the back, penetrating into the lobus posterior. DUDOK 

 DE Wit found, at the root of the arteria carotis interna and 

 in many other vessels of the head, firmly built, funnel-shaped 

 rings facing the bloodstream at their narrow end, and con- 

 sisting of radially-arranged elastic cells covered by endo- 

 thelium. Keibel (1926) found these rings also in Cyclos- 

 tomes and higher fishes, and is of the opinion that they serve 

 only to catch the rapidly streaming blood in the centre. In 

 view of the narrowed entrance, however, it seems to us that 

 their effect, on the contrary, would rather be to check the 

 bloodstream. 



c. The perihypophysial blood-sinus (Fig. ^2 and 53 J. 



Between the lobus intermedius and the lobus anterior a broad, 

 short vena afferens leaves the hypophysis dorsally (Fig. 52). 

 Thus the perihypophysial bloodsinus provides another source 



