CEREBRUM. 411 



more generally present, and to exist in the inferior animals. 

 They are generally longitudinal in their direction, while 

 the secondary are found to be mostly transverse. One of 

 the most regular of the primary convolutions, is the long 

 curved one situated on the inner or mesial side of each 

 hemisphere above, and separated from the corpus callosum 

 by a narrow furrow, which, from its surrounding the edge 

 of the hemisphere after the manner of a hem, is called the 

 ourlet or hem-like convolution ; it bends down in front with 

 the corpus callosum, and is lost in the inferior convolutions 

 at the Sylvian fissure, behind; it also follows the corpus cal- 

 losum, is attached to the posterior convolutions, and can be 

 traced downward and forward into the middle lobe form- 

 ing the hippocampus major. 



Another large primary one bounds the fissure of Sylvius, 

 and within this fissure is a cluster of radiated convolu- 

 tions called the " island of Eeil." 



The fissure of Sylvius is made a very important point by 

 Mr. Solly, as from one particular spot within it, called the 

 quadrilateral spot or substantia perforata anterior, all the 

 convolutions are made to arise. At this spot the hemi- 

 spherical ganglia are first observed as a mere point, and 

 from thence they gradually expand and develop themselves. 



Functions of the Convolutions. The convolutions are 

 regarded as the especial ganglia or instruments of the 

 mind, and comparative anatomy, experiments on living 

 animals, "developmental" anatomy, and pathology are all 

 brought to demonstrate most conclusively that the convo- 

 lutions constitute the especial cerebral organs of intel- 

 lectual action (for further remarks see nervous tissue, 

 under the head of Alphabet of Anatomy.) The cerebrum 

 contains a variety of bodies, which we will examine from 

 the base or below upward, as this is found to be the natural 

 order of development. 



The Crura Cerebri (Fig. 16) constitute the peduncles of 

 the upper brain, and are situated at the anterior or upper 

 edge of the pons. They are two in number and consist of 

 white, thick, fibrous cords about half an inch in length, round 



