280 J. S. FERGUSON 



('08), and Favaro ('09). Realizing the uncertainty which 

 attends the use of various silver methods one readily appreciates 

 the necessity for careful study of the effects of the method upon the 

 various tissue elements. Of the primary tissues epithelium and 

 other cells are scarcely if at all colored or have a faint brownish 

 tint; red blood cells darken readily and are either opaque black 

 or a deep brown according to the depth of the impregnation and 

 the duration of the toning bath; blood serum and intercellular 

 cement substance blacken, the latter appearing very granular; 

 all nuclei are an intense black, the silver reacting specially to the 

 chromatic portions, viz., nuclear wall, chromatin net and karyo- 

 somes; the axis cylinders of nerves are somewhat blackened, 

 though with the method employed the neuraxes are not nearly 

 so opaque as the fibers of reticular tissue. Muscle fibers blacken 

 irregularly depending on the depth of impregnation and they 

 show something of their fibrillar structure; the cross striations 

 and, in smooth muscle, the myofibrillae and intercellular bridges 

 appear beautifully shown in certain instances but it is possible 

 with care to have the muscle almost colorless and the reticular 

 fibers an opaque black. The silver apparently adsorbs somewhat 

 to the surface of muscle cells and elastic fibers and thus frequently 

 fills the interstices between fibers, forming an apparent inter- 

 fibrillar network in smooth muscle, in epithelium and in dense 

 elastic tissue, e.g., ligamentum nuchae. It is possibly this which 

 accounts for the apparent blackening of intercellular substance. 

 Both because of their reactions and because of their character- 

 istic differences of structure one has little difficulty in differenti- 

 ating these tissues after impregnation and distinguishing them 

 from the various types of connective tissue fibers. 



Before we can regard the method of Bielschowsky, applied to 

 tissues outside of the nervous system, as a specific stain for reticu- 

 lum, it is necessary to examine more carefully than has been done, 

 into the reaction of connective tissue fibers to the silver impregna- 

 tion and the differentiation, in sections prepared by this method, 

 of the collaginous, elastic, fibroglia and reticular fibers. Of the 

 fibrous tissues cartilage, bone, and dentine may be set aside be- 

 cause of their characteristic structure, obvious at a glance, though 



