284 J. S. FERGUSON 



while giving characteristic reactions to other stains. It is onl}' in 

 those locations where identification of elastic fibers is question- 

 able that one is inclined to suggest their identity with the black- 

 ened fibrils, but even then one sees indications of noticeable 

 difference. If a bit of areolar tissue is carefully examined in the 

 wall of the digestive tract, the skin, the peritoneum or elsewhere, 

 and sections of the tissue are also stained by the selective elastic 

 tissue stains, Weigert's, or Unna's, one observes on comparison a 

 difference in the number and arrangement of fibers selected by the 

 compared methods. The orcein and Weigert sections will com- 

 pare very closely. The Bielschowsky sections of the same series 

 frequently show many more fibers of the blackened type ; moreover 

 the blackened or reticular fibers are usually more wavy and of 

 irregular distribution, often having a typical spiral appearance 

 as compared with the relatively straight elastic fibers. This is 

 well shown in sections of collapsed or undistended lung in which 

 the elastic fibers of the alveolar walls and bronchioles are straight 

 while the reticular fibers, from the extreme contraction of the 

 organ, are thrown into a remarkably intricate network of wavy 

 and twisted fibrils, equally as distinct and more abundant than the 

 elastic. 



These findings are in confirmation of the views already expressed 

 by Woglom ('10) and others and appear to prove conclusively the 

 non-identity of elastic fibers with those fibers (reticulum) which 

 blacken in these preparations. This view is in accord with that 

 expressed by Mall ('02), who as a result of his comparison of the 

 tissues by chemical methods likewise demonstrated the non- 

 identity of elastic fibers and reticulum, but his studies of mesen- 

 chymal tissues showing embryonic stages of the connective tissue, 

 resulted in pictures delineating the first appearance of elastic 

 fibrils which simulate those which I have obtained in similar tis- 

 sues by the method of impregnation (fig. 4) . I shall consider this 

 phase of the subject in a later paper. At this time it is sufficient 

 to say that I consider the fibers referred to to be collaginous in 

 type. One must therefore finally emphasize the fact that in well 

 recognized portions of mature tissues elastic fibers in the silvered 

 preparations remain entirely colorless while reticular fibers 



