454 THE BRAIN OF MAMMALS, BY TH. MEYNERT. 



into the requisite co-ordination for determinate forms of move- 

 ment. The idea that such mechanisms for co-ordination would 

 betray themselves by anatomical features, has already been 

 advanced by Schroder v. d. Kolk, to whom it was suggested 

 by the appearance of the non-decussating origin of the nervus 

 abducens, as contrasted with the decussating origin of the 

 oculomotorius, to the significance of which we shall hereafter 

 revert. 



The fasciculi of each crusta, on the contrary, proceed en- 

 tirely from the ganglia of their own side, and, as we shall 

 presently show, they have, so far as regards the fasciculi of the 

 spinal cord, a common point of decussation in the course of the 

 pyramids of the medulla oblongata. 



The ganglia of the crusta do not therefore appear to be the 

 centres of co-ordination for definite forms of movement, through 



* O 



which, for example, unsymrnetrical muscles of the two sides 

 of the body act together. The grouping of the motorial acts 

 must necessarily be already accomplished by the centre that 

 centrifugally innervates the ganglion of the crusta ; that is to 

 say, by the cerebral lobes, through the agency of their arched 

 fasciculi acting as a connecting system. 



4. THE REGION OF THE INTERLACEMENT OF THE BRACHIA 

 OF THE CEREBELLUM WITH THE PROJECTION SYSTEM. 



It would be more correct to precede the description of this 

 region by that of the cerebellum, of that centre which is con- 

 nected with the projection system essentially by means of 

 transverse interlacing fibres, and by the intervention of grey 

 substance ; but I have not done so, because our knowledge of 

 the cerebellum is very faulty, and it will render the subject 

 more intelligible if it be not first considered, but if instead we 

 examine the connections of the cerebellum with other cerebral 

 organs, and thus place one aspect of this organ before our 

 eyes. 



The external form assumed by this territory of interlace- 

 ment of the projection system at the base of the brain 

 embraces the surface of the pons and the upper half of the 

 medulla oblongata. Very great differences occur both in re- 



