330 



Mr. B. Lewis on the Lymphatic 



[June 21, 



spindle form to be the natural and most prevalent. The fact seems to 

 be that the forms are too protean for any such exclusive statement to be 

 scientifically accurate. The fusiform cell is frequently seen in the third 

 layer, the pyramidal is also frequent in fresh specimens, others are pyri- 

 form, ovate, globose, or even so indefinite as to warrant the term 

 amcebiform. 



It will thus be apparent that the lymph-space surrounding the cell 

 must differ greatly in its contour. In some cases the lymph-sac is not 

 apparent, although its endothelial elements may indicate its existence ; 

 this, in all cases, I believe, is due to the mode of preparation, or to patho- 

 logical changes (probably, also, certain physiological conditions) not yet 

 satisfactorily investigated. Within these spaces we can frequently 

 detect the corpuscular elements of the lymphatic system, whilst a 

 faintly granular plasma remains as the representative of the coagu- 

 lated lymph. The boundary wall of these spaces varies much in appear- 

 ance, according to the character assumed by the surrounding matrix of 

 neuroglia. The more finely granular the appearance of the neuroglia 

 the less perfectly can the wall of the pericellular space be differentiated 

 from its environment, the minutest fibrils of connective and nerve inter- 

 mingled in the finely granular basis approaching to the clearly defined 

 margin of the space, and no distinct limiting membrane being observable. 

 In all probability these spaces are lined merely with a delicate endothelial 

 investment. In cases where great shrinking of structure has occurred 

 by the use of strong solutions of chromic acid and subsequent methods 

 of preparation, I have observed much distortion occur, whereby the cell 

 is laterally displaced, or even partially withdrawn from its enclosing sac. 

 The next stage in my observations was arrived at by the discovery that 

 a minute blood-vessel invariably ran in close contact with all the large 

 nerve-cells. In some cases the elongated nuclei of the capillary might 

 not have been sufficiently stained and the outline of the vessel not dis- 

 tinct, yet the line of perivascular endothelial elements would unmis- 

 takably indicate its course, except where the vessel had been cut across, 

 when the open lumen surrounded by its perivascular sheath, often with 

 one or more nuclei attached, still indicated the close proximity of the 

 vessel to a nerve-cell. 



In all cases I have never failed to recognize, on careful examination, 

 a small capillary either passing immediately across the nerve-cell or 

 running with a gentle curve along the confines of the pericellular space. 

 The invariable occurrence of this arrangement naturally struck my at- 

 tention as a highly significant fact, and more extensive observations 

 proved it to be the universal arrangement throughout the cortex cerebri. 

 In many instances a distinct connexion between perivascular and peri- 

 cellular space could be clearly observed, although from obvious reasons 

 the majority of specimens exhibited this connexion only after the most 

 careful and strict scrutiny, or afforded, on the other hand, no definite 

 indications of its existence. 



