184 Observatiom on the Structure of the Brain. 



others, — from a total ignorance with regard to the disposition 

 of the elementary texture in which the nervous matter of the 

 brain has been generally believed to be contained, — from the 

 supposition that has prevailed that a fluid or mucous matter 

 might constitute the matrix in which the nervous filaments are 

 deposited, — and from the circumstance that fibres of very differ- 

 ent magnitude have been looked for in the nervous texture by 

 different observers. 



Professor Ehrenberg has shewn that the proper nervous sub- 

 stance of the Brain and Nerves does actually consist of very 

 minute fibres ; and he informs us that these fibres can only be 

 discovered by the aid of a magnifying power of 300 diameters, 

 and that he was sometimes obliged to have recourse to a much 

 greater magnifying power, as 800 diameters, in order to bring 

 them into view. He examined thin slices of the recent brain, 

 and states that the fibrous structure was in general most obvious 

 at the thin margins of the slices, when these were simply laid on 

 the object glass-holder of the microscope, and that gentle pres- 

 sure of the nervous substance between two thin plates of glass 

 generally rendered the fibres more apparent. 



The great mass of the Cerebrum and Cerebellum consists, 

 according to Professor Ehrenberg, of very minute fibres irre- 

 gularly disposed in the cortical part, and there interspersed 

 with globules and plates, converging as they pass inwards from 

 the surface towards the centre of the brain. The greater 

 number of these fibres have not a regular cylindrical shape, 

 but present the appearance of strings of pearls, the swelled 

 portions being situated at some distance from one another, 

 and united by narrower parts which are continuous with them, 

 and are formed apparently of the same material. Besides these 

 fibres, which Professor Ehrenberg calls articulated, from their 

 knotted appearance, this observer states that towards the base 

 of the brain and crura cerebri, other somewhat larger fibres, 

 of a regular cylindrical form, are to be observed, interspersed 

 among the articulated or knotted ones. These two sets of fibres 

 are not held together by cellular tissue, nor fluid, nor mucous 

 matter, but appear to be nearly in juxtaposition with one an- 

 other, except where they are penetrated by the net-work of mi- 

 nute bloodvessels which are every where "distributed through 



