16 Development of Blood-Vessels of Himian Brain 



The superior sagittal sinus is formed by an accumulation of small 

 veins over the dorsal side of the cerebral vesicle (Fig- 3), which some- 

 times appear as a tuft (Fig. 13) and at other times as a lakelet (Fig. 

 9). Soon the sinuses of the two sides communicate (Fig. 10), and from 

 now on the paired sinuses are single. At first the sinuses com- 

 municate witli tlie anterior cardinal vein (the cavernous sinus) through 

 the vena cerebralis anterior, and these two veins take up all of the small 

 veins from the cerebral vesicle (Fig. 10). With the growth of the 

 cerebrum the superior sagittal sinus is shifted downwards and its 

 communication with the cavernous is broken. It now communicates 

 with the vena capatis lateralis through the vena cerebralis media, a tran- 

 sitional form being shown in Fig. 10. With great rapidity the commu- 

 nication is transferred to the jugular through the vena cerebralis pos- 

 terior, which leaves the skull through the jugular foramen. This stage 

 is shown in part in Fig. 11, which is a reconstruction from a partial 

 natural injection. However, even in this case the superior sagittal 

 sinus must be shifted more dorsalwards, for in this embryo it still 

 passes lateral to the otic vesicle, and therefore in this region it is outside 

 of the skull. The same criticism can be made of Salzer's figure of the 

 corresponding stage in the guinea-pig." Here also the vena capatis 

 lateralis, as well as the first dorsal anastomosis, is lateral to the otic 

 vesicle, and therefore cannot possibly be the permanent vein in this 

 animal. In order to reach, the permanent form, as shown in Salzer's 

 Fig. 5, a second dorsal anastomosis must be established, and this is 

 well begun, as Salzer's Fig. 4 shows. So in order to complete the super- 

 ior sagittal and transverse sinuses a more dorsal anastomosis must be 

 established than that shown in Fig. 11, and the indications for this are 

 present in this figure, as well as in Fig. 10. In this latter figure the 

 superior sagittal sinus must be transferred completely from the vena 

 cerebralis anterior to the vena cerebralis posterior, and in so doing 

 the vena capatis lateralis is obliterated. In case they all remained open, 

 we would have the condition found in Tropidonotus," but this is not the 

 case, as is indicated in Fig. 11. The complete condition of the superior 

 sagittal sinus is shown in Fig. 8. Here the internal jugular com- 

 municates through the vena cerebralis posterior with the dorsal end of 

 the superior sagittal sinus along the line of the hind-brain and mid-brain. 

 The steps towards this are all indicated in Fig. 10. Therefore the main 

 portion of the transverse sinus is formed directly from the vena cerebralis 

 posterior. 



"Salzer: Morph. Jahr., XIII, Taf. XVIII, Fig. 4. 

 "Groszer and Brezina: Morph. Jahr., XXIII, Taf. XXI. 



