44 C. ]V. -1/. Po y liter 



nicnts of these fissures so clear that there is no probabiHty of con- 

 fusing tliem with others. Communication may be estabhshed be- 

 tween the fissura calcarina and the fissiira hifpocampi in rare 

 cases, as mentioned above. Connection between the fissiira rhin- 

 alis and the collateral is frequent. Duckworth (1907) finds it 

 present in 50 per cent, of Australian aborigines. He thinks a 

 boldly curved fissura rhinalis, a condition found in the Simiidae, a 

 distinctive mark of the lower type of human cerebrum. 



Fissura Collatcralis: Sergi (1911) has made a study of the 

 fissure elements situated below the calcarine fissure and divides 

 the area into three distinct zones, viz.. anterior, intermediate 

 and posterior. The intermediate is the most extensive and the 

 anterior and posterior are very variable in orientation and 

 extent. (This division agrees with the work of Brodmann.) 

 He tinds that the collateral fissure constantly shows a single 

 fundamental element found behind the fissura rhinica and 

 often some distance from it. Posteriorly it is often in confluence 

 with elements of the lingual or sublingual region ; at times it is 

 continent with the posterior extremity of the sulcus temporalis 

 inferior, often with accessory sulci of the gyrus fusiformis (that 

 is, elements representing the subcalcarine region [Sergi]), or the 

 sulcus occipitalis inferior. Anteriorly the tissura collateralis may 

 be joined by the sulcus temporalis inferior, and either of these fis- 

 sures or their common stem anastomosed with elements repre- 

 sented in the anterior zone already referred to. The elements of 

 the posterior zone vary in number and arrangement and may 

 establish beside the communications already referred to. those with 

 the calcarine fissure. 



Sulcus Temporalis Inferior: This sulcus Sergi has also studied 

 in its relation to the collateral. He finds them separated by the 

 gyrus fusiformis with a possible continence behind already re- 

 ferred to. Anteriorly, confluence may occur with the unstable 

 elements temporo-polari (Sergi) of the region just discussed 

 (regio temporo-occipitalis inferior [Sergi]). Sergi (1911) says 

 of the anterior and posterior zones, the tempcro-poJari segments 

 turn into the temporo-polari region which extends into the 

 region of the temporal pole and meets caudally the temporal 



388 



