LECTURE IV. ' 109 



central lobe; hence tliey have been called the central, or interme- 

 diate^ convolutions. They are separated by a deep fissure, which 

 is easily seen in most brains, even when viewed from above. 



We look upon these central convolutions as an important 

 part of the brain ; but we cannot agree with the meritorious 

 Huschke when he says, " After what I have shown of the de- 

 velopment of the convolutions, there can be no doubt that the 

 point of indifierence in each hemisphere is to be found in the 

 central convolutions. Their central, indifferent signification is 

 known by their central position (in the centre of the sagittal 

 suture), their great size, and the depth of the central fissure 

 which separates them, their simplicity and regularity, and 

 finally, from their manifold connexions with their six to 

 eight arms, which radiate to different sides, like wires bring- 

 ing telegraphic messages from all parts of our mental organs to 

 these chief convolutions, or receiving orders from thence. Here 

 is the watershed whence the longitudinal convolutions flow north 

 and south, forward and backwards; or the common bed into which 

 the different branches empty themselves. With their formation 

 in the ape, the brain enters the last stage of development until 

 it arrives at its perfection in man, beyond which stage it cannot 

 pass, having gained the object of its development, — a distinct 

 point of indiffei'ence with its connecting poles. In those mam- 

 mals in which these large convolutions are absent, the two poles 

 are like the anterior and posterior halves of three superimposed 

 horseshoes fused together. In the brain of man, they first 

 become divided by a partition in the shape of central convolu- 

 tions, — just as the heart does not reach its highest stage of 

 development until a septum is acquired, so that red and black 

 blood are divided from each other. The great influence of this 

 polarity of the blood is shown by animal heat. The organism, 

 hitherto cold-blooded, becomes in the class of birds, almost at 

 once, warm-blooded. A similar, though as yet unknown in- 

 fluence must be exercised on the mechanism of nervous activity 

 by the central convolutions. Determination, acuteness, perspi- 

 cuity, greater unity of psychical life must be connected with it." 

 Really, this is carrying polarisation a little too far. Let us 

 return to our convolutions. 



