158 SUMMARY OF CURRENT RESEARCHES RELATING TO 



covering one of tlic vertical faces of this cube (the one turned in 

 the direction of the knife) with a thin coat of soft i)arafHn, which 

 insures the adherence of the sections to one another by their 

 edges. 



Dr. C. 0. Whitman also points out * that it is important to use a 

 moderately soft paraffin, which may bo obtained by mixing in proper 

 proportions soft and hard jiaraffin, and further to give the piece of 

 paraffin to be cut a rectangular form. The jiiece must then be so placed 

 in the holder that the side next to the knife is exactly parallel with 

 the cutting edge. Thus placed, every section lies flat on the blade. 

 The second section pushes on the first, adhering to its adjoining side ; 

 the third pushes on the first two, adhering to the second. A whole 

 ribbon of sections may be cut in this way in a fcAv moments without 

 danger of losing their serial order. Thus three very important points 

 arc gained : the sections remain perfectly flat, the cutting may be as 

 rapid as the hand can move, and the order of the sections is preserved 

 without trouble to the manipulator. Care must be taken only that 

 the opposite sides of the paraffin are parallel, otherwise the ribbon 

 will curve to the right or left and the arrangement of the sections on 

 the slide be less easily accomplished. 



New Application of Haematoxylin.f — E. Heidenhain describes a 

 process which gives an entirely different stain to that of the ordinary 

 fluid. The iugi-edients are a 1/2-1 per cent, aqueous solution of 

 ha3matoxylin and a 1/2-1'per cent, solution of bichromate of potash. 

 Small pieces of tissue well hardened in alcohol are first placed in 

 8-10 c.cm. of the former fluid, and after 8-10 liours for the same time 

 in a nearly equal quantity of the second solution. After they have 

 taken a black colour throughout, the excess of bichromate of potash is 

 removed by water. Then follows dehydration by alcohol, imbedding, 

 &c. The sections must be cut extremely thin. 



The nuclei are mostly black, and the tissue-elements a more or 

 less dark grey or also black, but so that difix^rent elements take an 

 entirely different shade of grey and arc readily distinguished as if in 

 an artistically finished woodcut. In epithelial tissue the outlines of 

 the cells are extremely sharp. In the separate cells the protoplasm is 

 darker than the other contents, so that the richness of different cells 

 in protoplasm and its distribution in the separate cells is admirably 

 shown. The markings of the primitive bundles and fibrillse in 

 muscle are much clearer than in the fresh tissue. Nerve-fibres are 

 also well shown. 



A blue stain is obtained if instead of treating the tissue with 

 bichromate of potash, a 1 per cent, alum solution is used. 



Weigert's Staining Method for the Central Nervous System. — 

 C. Weigert, in 1882, described + a method of staining the central 

 nervous system in which acid fuchsin was used, and which left the 



* Amer. Natural., xviii. (1884) pp. 106-7. 



t Arch. f. Mikr. Anat., xxiv. (1884) pp. 468-70. 



t Ccntralbl. f. d. Med. Wiss., xx. (1882) jip. 753, 772, and 819. 



