312 LECTURE XIII. 



ventricles of the brain, but only an epithelial covering, 

 the epithelial cells directly resting upon the surface of 

 the horizontally disposed nerve-fibres. This epithelial 

 layer was what Purkinje called ependyma ventriculo- 

 rum.* This assumption, it is true, was never shared in 

 by pathologists. Pathological observation held on its 

 course pretty unconcernedly by the side of these histolo- 

 gical assertions. However, it appeared desirable that 

 some understanding should be come to on the subject, 

 since in a merely epithelial ependyma an inflammation 

 would scarcely take place, like that which is wont to be 

 attributed to serous membranes. The result of my in- 

 vestigations was, that there certainly does exist a layer 

 beneath the epithelium of the ventricles, which in many 

 parts has quite the character of connective tissue, but in 

 other places possesses great softness, so that it is ex- 

 tremely difficult to give a description of its appearance. 

 Every, even the slightest, traction of the part alters its 

 appearance, and a substance now granular, now striated, 

 now reticulated, now of any other form, is seen. 



At first I thought I had succeeded in showing that a 

 tissue analogous to connective tissue did actually exist in 

 this part, and that the presence of a membrane could be 

 demonstrated. But, the more I occupied myself with 

 the examination of it, the more did I become convinced 

 that a real boundary between this membrane and the 

 deeper layers of tissue did not exist, and that a mem- 

 brane could only be spoken of improperly, inasmuch as 

 the notion of a membrane involves the supposition that 

 it is more or less different from the parts beneath it, and 

 constitutes a separable object. Now in the present 



* This term has had its signification extended by the Author, who takes it to 

 include the whole of the layer (connective tissue as well as epithelium), which rests 

 upon the nerve-fibres and is interposed between them and the cavity of the ventri- 

 cles. From a MS. Note by the Author. 



