Clark, Comparative Anatomy of the Insula. 73 



gyres upon its surface are also distinct and not dependent upon 

 those of the rest of the cerebrum. 



5. The central fissure is not known to exist outside of the 

 primate brain, while, as will be shown, the transinsular fissure 

 is present in many imprimates and the relation of the transinsu- 

 lar to the Sylvian in them is sometimes as in man (see raccoon); 

 but more often it coincides in position and direction with the 

 Sylvian fissure. 



6. The transinsular fissure gradually becomes less deep as 

 it approaches the circuminsular fissure dorsad, and it has never 

 been shown to extend beyond this fissure, while in some im- 

 primates it never reaches the dorsal margin of the circuminsular 

 fissure. 



7. The central fissure is sometimes double ; the writer 

 has been unable to find a single recorded instance of the dupli- 

 cation of the transinsular fissure. 



8. The reasons given by Cunningham (13, 287) to show 

 that because the preoperculum is (as he thinks) absent in the an- 

 thropoid it necessarily follows that a portion of the insula is 

 also absent, are not well founded. The human insula has near- 

 ly or quite the same form before as after the appearance of the 

 preoperculum and the writer fails to see why it should be oth- 

 erwise in the ape. 



9. The mononym "transinsular" fissure (Wilder) indi- 

 cates better the relation of this fissure to the insula and is far 

 preferable to the polyonym "sulcus centralis Reilii " of Guld- 

 berg and Cunningham. 



The blood-supply of the insula is derived from the branch- 

 es of the medicerebral artery which ramify over its surface. 

 The main branch lies in the transinsular fissure as shown in 

 Fig. 4. From these branches small arteries penetrate the cor- 

 tex directly. 



THE RELATION OF THE INSULA TO THE CLAUSTRUM. 



On account of its intimate connection with the brain-stem, 

 the insula has been called the stem-lobe or Stavimlappen. En- 

 tad of the insular cortex (see Fig, 6) but separated from it by 



