68 

 thDf'is to knob;? and mush room-like excrescences which rise far 

 ^bove the general level. The extent of receptive surface of 

 the entire deniritic series is thus increasei to a very con- 

 si:ierable degree. 



The part «hich the neurone of Purkinje takes in the econ- 

 omy of Mustelus will be discussei in Subsection 5. 



2. The Holeoular Layef. 



This is the external layer of the cerebellum (^ig. 1?, m.l. ), 

 It conforms throughout to the contour of the several folds 

 into which the cerebellar wall is thrown. Its tnickness is 

 carried flith considerable uniformity, but in most of the re- 

 gions the depth of matter is only about half as much as that 

 of the granular layer within. 



The molecular layer is characterized by the predominance 

 of fibrous elements and the fewness of nerve-cells. In con- 

 trast with the mass of densely-packed, conspicuous cells of the 

 granular layer, the outer region presented hardly more than a 

 minutely punctate appearance to the earlier investigators who 

 had recourse to nothing more differential than the general 

 stains in use at that time. Hence moleaular seemed an appro- 

 priate descriptive term for this layer. 



Through the use of modern methods, we find the molecular 

 layer to have a few proper neurones of small size, but the 

 great mass of substance consists of fibrous material, between 



