446 Journal of Applied Microscopy. 



The writer has previously published in 

 Bolton, J. S. On the Raneeof ApplicabDitv of ^, . ,. , ,._ ,,^ ^^r. ^ 



Certain Modifications of the Weigert-Pal the same periodical (32: 24/ -266,) a 

 process. Journ. of Anat. and Physiol. 33: N. discussion on the application of the 

 V ., 13, pp. 292-300, 5 ps., I 99. Weigert-Pal method as applied to for- 



malin hardened tissue, and in the present paper treats of the relative merits of 

 certain modifications and the range of their applicability. All material is hard- 

 ened in five per cent, formalin and is prepared by the osmic acid, iron-alum, or 

 ammonium-molybdate methods earlier described. In regard to the relative merits 

 of the three methods the author says that for the coarser nervous tissue — for in- 

 stance, human — osmic acid is invaluable, owing to its blackening the medullary 

 sheaths. In finer tissue or with non-meduUated fibers, as in the minnow, results 

 are inferior. Iron alum with the author proves a most successful mordant. Axis 

 cylinders and medullary sheaths are deeply stained, and especially fine fibrils, as 

 in the case of small fishes, are well worked out ; occasionally nerve cells are also 

 finely stained. Sections require careful washing between the iron-alum and log- 

 wood bath, and the iron-alum solution should be freshly prepared and not used 

 a second time. Ammonium molybdate is most satisfactory in its results, and 

 with a yellow screen sections will photograph well ; it is not as satisfactory for 

 the finest fibers as iron alum, owing to its fainter color. The bath can be used 

 repeatedly, however, but sections must be hastened through the alcohols. Osmic 

 acid is the weakest mordant of the three, it is the least likely, with care, to stain 

 bare axis cylinders or collaterals. Iron alum is the most powerful of the three, 

 staining all the nervous network including nerve cells. The chief conclusion 

 drawn by the author from his experience, is that the Weigert-Pal process is not a 

 specific method for staining medullated fibers with haematoxylin, but dyes fibers 

 exclusively after three steps, mordanting the fibers, forming a lake in them and 

 finally removing the stain by oxidation from nearly all the other parts of the com- 

 plex tissue. Only those parts of the tissue possessing a high degree of metabolic 

 activity take the stains and react to the different steps, so a difference on results 

 is readily explicable. Reference to the photomicrographs with which the article 

 is illustrated shows that the methods are applicable to the human cerebral cortex, 

 brain, cord, peripheral nerves and ganglia of mammals, and the nervous system of 

 the frog and fish. Hence it is clear that the Weigert-Pal method is capable of 

 wide application without much modification. a. m. c. 



Krompecher, E. Beitiage zur Lehre von den '-^^'lese studies were carried out on dif- 



Plasmazellen. Beiir. zur pathol. Anat. u. ferent kinds of pathological material. 



zur allegem. Pathol. 24: 16^-182, i pi, i8g8. ,1,1 1 • n > r r • 1 



"^ ' ^ Alcohol was chieny used for fixing and 



hardening, sometimes also sublimate. Sections were stained in methylen blue 

 (polychromic) and thionin, and decolorized with alcohol or glycerine-ether ac- 

 cording to Unna. Both methods were equally successful. Sections were stained 

 in methylen blue from a quarter of an hour to over night, and after washing in 

 water were brought direct into the glycerine mixture for about fifteen seconds, 

 when differentiation is complete ; washed carefully in water, and in absolute alco- 

 hol and bergamot oil, and mounted in balsam. For demonstrating the basophil 

 granules the author used, besides the conventional polychromic methylen blue, 



