TISSUES OF THE BODY. 



197 



Fig. 188. Connective- 

 tissue sustentacular 

 matter from the pos- 

 terior pillars of the hu- 

 man spinal cord, sur- 

 rounding sections of 

 the nerve-libres. 



nective-tissue to exist in large quantity in the nervous centres, while 

 other investigators deny almost completely the presence of any other than 

 nervous form-elements in those organs. 



Wherever the connective-tissue framework is well developed, and to a 

 certain extent pure, as is the case in the " ependyma" 

 (so named by VircJiow) of the ventricles of the brain, 

 and in the matter lining the central canal of the 

 cord, it occurs as a more or less homogeneous or 

 streaky or fibrillated mass, in which ordinary radiated 

 or fusiform cells are seen to be imbedded. 

 This substance, whose connective-tissue character 

 cannot conveniently be doubted, is continuous then 

 with the sustentacular substance of the white and 

 grey mass, a far more difficult subject for investiga- 

 tion namely, with the so-called " nerve-cement " or 

 " neuroglia " of Vircliow. 



If we examine a portion of the white substance of the brain which has 

 been hardened artificially, we see how the fibres are separated from one 

 another by bands of such a substance. 



This may be either homogeneous or streaky; and in it are situated, 

 at intervals, round or oval nuclei, smooth in contour, and measuring 

 0*0093-0'0075 mm. We learn also, from side views, that these septa, 

 seen in the transverse section, are continued further between the nervous 

 cylinders as membraniform prolongations, so that in this way a regular 

 system of tubular compartments is formed. The elements of form, of 

 which the latter is composed appear to be cells with radiating processes, 

 spreading out into membraniform prolongations and investing masses. 



But the sustentacular tissue of the grey 

 matter of the nervous centres, though much 

 more abundant, is far more fragile and difficult 

 to elucidate. In fresh preparations it is found 

 usually as a rather granular complementary 

 matter, filling up the interstices between the 

 nervous fibres and cells. It sometimes con- 

 tains but a few, sometimes, however, very 

 many, nuclei with smooth contour, and measur- 

 ing -0090- 0-0075 mm. In successfully-treated 

 preparations (fig. 189) we recognise, with the 

 aid of extremely powerful lenses, a wondrously fine and dense network of the 

 most delicate fibrillae, which take their rise from knots, in each of which 

 one of these nuclei lies imbedded, not unfrequently enveloped in a thin 

 layer of pro topi asma. Here again we may have before us a network of 

 stellate cells in this porous spongy tissue. But the pre-existence of such 

 a network, though very probable, is not yet capable of proof, and the 

 possibility of the tissue before us being an artificial fabric must be 

 admitted. 



This porous supporting substance, with its cellular equivalents, is, 

 moreover, traversed at points by definite fibres of connective- tissue. 



The connective-matter of the retina appears precisely the same, the 

 supporting fibres of which are known under the name of Mutter's fibrillas. 



In that extraordinary fatty organ, the so-called thymus gland of hiber- 

 nating animals, which occurs in many of the Mammalia, we meet with a 

 similar dense network of the finest fibres in hardened preparations. 



Fig. 189. Spongy tissue from the 

 grey substance of the human 

 cerebellum, obtained by treat- 

 ment with very dilute chromic 

 acid. 



