260 MORPHOLOGY OF THE CEREBRAL CONVOLUTIONS. 



C. INFERIOR SURFACE. 



X. Dentate lobule (Gezahnterwulst). 



18. Detitate convohition. 



XL Inferior mesial long lobule (Langs wulst). 



19. Inferior mesial long lobule convolution 



XII. Inferior lateral long lobule. 



20. Inferior lateral long lobule convohition. 



In this way Pansch divides the hemisphere into three surfaces, sub-divided into 

 twelve lobules and these in their turn into twenty separate and distinct convolu- 

 tions. We shall consider the morphological value of these sub-divisions hereafter. 



In 1870, Bischoff 1 published a plan or type according to which he believes 

 the fissures and convolutions are arrayed. He considers that a large number of 

 the convolutions of the great hemisphere are arranged around the ends of the pri- 

 mary furrows in more or less simple or complicated arches. The primary fissures 

 according to him, are the anterior and posterior branches of the fossa Sylvii. the 

 fissura centralis, the fissura perpendicularis interna, the fissura parallela and the 

 fissura hippocampi. This latter fissure of Bischoff corresponds to the one of the 

 same name of Gratiolet (scissure des hippocampes) and includes both the fissura 

 hippocampi and the fissura calcarina of most other writers. The type is expressed, 

 according to his view, by these fissures, and the development of the convolutions 

 consists merely of arched windings around the ends of these primary furrows ; 

 whilst the further development of the convolutions arises in fact, through the 

 stronger development, bending backward and forward, rising and sinking of the 

 lobules around the above named furrows. Through this process there arise second- 

 ary folds and fissures, side convolutions, connections and separations of individual 

 convolutions. These, says Bischoff. may be different on the two sides of the 

 same brain and in different individuals, the ground form being, therefore, more or 

 less hidden, but we can recognize them easily in all brains. He hopes, however, 

 that it will soon be possible to explain and make intelligible these individual modi- 

 fications. There are, however, convolutions which, as Bischoff admits, do not 

 appear to be in unision with this type, such as the first and second frontal 

 and the convolutions of the occipital and temporal lobes. He can find no 

 particular plan on which these may be based. They arise one after the other and 

 become more and more complex, as it appears, from the purely mechanical necessity 

 of the surface increasing in a definite space. In this manner arise the first and 

 second frontal fissures, the second temporal, the fissura collateralis, etc., and 

 their accompanying convolutions. Thus in the frontal lobe, Bischoff points out two 

 upper frontal convolutions and a third or inferior arching around the ascending 

 branch of the fossa Sylvii. In the parietal lobe, an anterior and a posterior 



1 Die Grosshirnwindungen des Menschen, etc. 



