Irving Hardesty . 255 



sidered neuroglia fibers or, at least, not as adult neuroglia fibers. They 

 may develop their chemical difference later. On the other hand, some of 

 them may be threads of the white fibrous connective tissue which are sup- 

 posed never to color as neuroglia fibers. 



In Fig. 12 is shown an area containing fibers, some of which are begin- 

 ning to develop their chemical difference from their surroundings. Fig. 

 13 is from a suckling pig of about two weeks. The following are some 

 of the steps in the transformation indicated. 



After the medullation has begun, the syncytium, now merely moulded 

 into the interspaces of the nerve-elements and blood-vessels, begins to 

 show appearances indicative of the adult form. Nuclei situated in the 

 larger interspaces have pressed about them a more compact protoplasm 

 which shows slight granulation (endoplasm). These masses are contin- 

 uous with those in neighboring spaces by necessarily more or less atten- 

 uated portions of the syncytium (exoplasm), which appear more fibril- 

 lated than the portions immediately about the nuclei (see a, Figs. 12 and 

 13). Whether in large or small masses, the more fibrillated portion of 

 the syncytium stains less deeply than the more granular areas. Its 

 occurrence is probably the first evidence of the transformation of the 

 tissue, for it is often apparent that the more deeply staining form, 

 usually about the nuclei, is being converted into the less deeply staining 

 form. When the " free nuclei " occur in spaces large enough to afford 

 an appreciable amount of the more deeply staining protoplasm about 

 them, it may be assumed conversion has occurred {d. Fig. 12). 



The more lightly staining portion of the syncytium may be considered 

 l^refibrous tissue, for it is this which becomes transformed into the neuro- 

 glia fibers. If the special neuroglia stain can be trusted to express the 

 process, the transformation is interesting. First, more evident fibers 

 appear in the section, seemingly formed by a condensation of the less 

 deeply staining substance. These fibers are of various lengths and usu- 

 ally their course is more or less straight. They may pass through the 

 domain of more than one nucleus. Instead of staining the characteristic 

 blue of neuroglia fibers, most of them stain only a more dense shade of 

 the color of the general substance. However, in the same section some 

 also may be seen undergoing the chemical transformation (/, Fig. 12). 

 In such a fiber a portion only may give the blue reaction, while another 

 portion may stain indistinctly blue or not at all. Close examination 

 sometimes reveals something like a line of fine dots {e, Fig. 12). These 

 fibers vary but little in size and are but little smaller than those found 

 in the adult. 



