328 Mr. B. Lewis on the Lymphatic [June 21, 



appreciate the significance of this arrangement of nuclei around these 

 cells it will be necessary shortly to consider the actual cell-elements 

 which enter into the formation of the non-nervous portion of the 

 neuroglia. These elements are usually stated to consist of free nuclei 

 and distinct nucleated cells. The nuclei of the latter are said by Meynert.* 

 to have a diameter of 9 — 10/z ( = -009 to '010 millim.), a measurement 

 which coincides with my own. I find these last-mentioned cells possess 

 an extremely delicate protoplasm, so readily affected by reagents that it 

 is easily altered in appearance or entirely masked from yiew. Within 

 these cells two nuclei are frequently seen. These cells, in certain morbid 

 conditions, proliferate freely, and throw oat delicate and anastomosing 

 branches in all directions, assuming the form of " Deiter's cells." They 

 are undoubtedly connective elements, and by this morbid proliferation 

 they produce a true sclerosis of the cortex ; such a condition is deli- 

 neated in Plate 2. fig. 5. This morbid growth of the nucleated cell in the 

 neuroglia is alluded to by Meynert as bearing a relationship to arrest in 

 the discharge of the perivascular lymph, as would occur in hyperemia 

 and also in degeneration of the lymphatic glands of the head and neck. 

 I have myself frequently observed these changes in tuberculosis and 

 senile atrophy of the brain. It must be borne in mind that such a growth 

 must still further impede the current in the perivascular channels by the 

 intertwining of then numerous branches around the walls of the delicate 

 capillaries of the cortex. 



It is important that a distinction be drawn clearly between these cells 

 and the other nuclear elements referred to. These, the so-called free 

 nuclei, are not in reality free nuclei : for when examined carefully in the 

 fresh state they are found to have a slight delicate investment of proto- 

 plasm, which becomes quite destroyed by subsequent methods of pre- 

 paration. These nucleus-like bodies resemble, as regards size, form, 

 structure, and reaction to staining and chemical reagents, those which 

 are found universally scattered through the brain, and which most 

 observers, I believe, accept as representatives of the connective-tissue 

 series. Now these elements appear to me to be disposed in three 

 definite situations : — a, irregularly in the neuroglia f/amework ; b, re- 

 gularly around the nerve-cells ; c, following directly the course of 

 capillaries. 



In the two last positions they are connected with the lymph-walls 

 surrounding the blood-vessels and nerve-cells, and I am disposed to re- 

 gard them as endothelial elements lining these channels. The spindle- 

 cell of the deepest cortical layer in the frontal region appears to be 

 especially prone to the growth of these attendant satellites, which accu- 

 mulate occasionally in such numbers as to form superincumbent heaps, 

 almost concealing the nerve-cell from view. 



Frequently the capillary is so faintly stained that we can trace its 

 * Strieker's ' Histology ' (Sydenham Society), vol. ii. 



