ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
817 
of pure methylen-blue. The pigment is dissolved in physiological salt 
solution. The stain is fixed by means of the iodide and iodine solution 
or Hoyer’s picrocarmine. 
Such preparations are examined and mounted in glycerin. If, 
however, the pieces are imbedded, then platinum chloride must be used 
as fixative, since the picrocarmine and iodine are easily dissolved out 
by the various reagents used for imbedded specimens. 
A still better method is to fix with picrocarmine for fifteen minutes, 
followed by one per cent, osmic acid for the same time, and then 
glycerin for some hours. The specimen can now be imbedded by the 
gum arabic method. This consists in taking a watchglassful of a 
solution of jrnre gum arabic having the consistence of thick syrup. To 
this are added six to ten drops of glycerin, and the whole stirred up 
with a glass rod. In this mixture the sections are placed and the whole 
left to dry until it has assumed a consistence suitable for cutting (about 
eight days). The imbedded object is then clamped in elder-pith and 
sectioned. 
The chief objection to this method is that when the mass has acquired 
the proper consistence it must be cut at once, otherwise it becomes too hard. 
New Method for Staining Sections of Central Nervous System.* — 
For staining sections of central nervous system, A. Breglia uses extracts 
of Campecliy or Pernambuco wood. The former contains h£ematox 3 T lin 
C 16 H u 0 5 , the latter brasilin C 2 2 H 20 O 7 . 
The extract is made as follows: — 7 to 10 grm. of the^wood in small 
pieces are soaked in 90 to 95 per cent, alcohol for five or six days. The 
mixture is then shaken up and the fluid is ready for immediate use. 
Sections of nervous tissue hardened in Muller or Erlizki's fluid are 
placed for ten to fifteen minutes in 15 ccm. of 90 per cent, alcohol to 
which has been added three to seven ccm. of a saturated aqueous solution 
of neutral acetate of copper. The sections are next immersed for five to 
ten minutes in a saturated watery solution of lithium carbonate. They 
next come into ten ccm. of the extract for 18 to 24 hours. Decoloration 
is then effected with aq. dest. 100 grm., ferricyanide of potash 1 grm., 
borax 1 grm. When the grey and white matters have become differen- 
tiated to the naked eye, the sections are washed in distilled water, and 
then mounted in the usual way. For the Pernambuco wood extract, the 
method of manufacture and the manipulative procedure are the same, 
with the exception that the decolor izer acts very much more rapidly. 
Staining Central Nervous Tissue with Palladium Chloride.* — Prof. 
G. Paladino recommends the chloride of palladium for staining sections 
of the central nervous system. The procedure is as follows: — To a 
1 per thousand solution of chloride of palladium a few drops of hydro- 
chloric acid are added in order to insure its complete dissolution. 
In this solution pieces of spinal cord 5 mm. thick are immersed. 
The cord has of course been previously hardened in bichromate salts, 
chromic acid, or in sublimate. In the palladium solution, of which a 
large quantity (150 to 200 ccm.) are used for each piece, the objects are 
* Giorn. d. Assoz. dei Naturalisti e Medici di Napoli, i. (1889) pp. 169-72. Cf. 
Zeitschr. f. Wiss. Mikr., vii. (1890) pp. 236-7. 
t Journ. de Micrographie, xiv. (1890) pp. 142-8. 
