404 NERVOUS SYSTEM- GENERAL METHODS. 



oblongata, and pons, 5 per cent, for cerebellum, and 4 per cent, for 

 cerebrum. 



The methods of BEVAN LEWIS (op. cit.) and HAMILTON (Journ. 

 Anat. and Physiol., 1878, p. 254) can be considered as superseded, 

 chiefly because they are based on a fixation with methylated spirit 

 (Bevan Lewis) or mixtures of Miiller's fluid and methylated spirit 

 (Hamilton), which cannot be used any longer for histological pur- 

 poses, owing to the excess of impurities it now contains. Also the 

 methods for encephala of DUVAL (Robin's Journ. de I' Anat., 1876, 

 p. 497) and DEECKE (Journ. R. Micr. Soc., 1883, p. 449) can be 

 considered as obsolete. 



ORTH uses formol-Muller changed every few days. See 113. 



BONVICINI (Ztschr. wiss. Mikr., xxvi, 1909, p. 412)' puts entire 

 human brains into 10 per cent, formol (first injected through the 

 carotids or into the ventricles) for six to eight days, cuts them into 

 1 cm. thick slices by means of a special macrotome, and transfers 

 them into a mixture of 4 parts of potassium bichromate and 2-5 parts 

 of chromium sulphate in 100 of water, and keeps them therein, in the 

 dark, for two months for cerebral hemispheres, twelve to fourteen 

 days for medulla and pons, five or six days for spinal cord. In the 

 case of slices of brain, the fluid must be changed every week. 



KAWITZ (ibid., p. 338) puts formol material for exactly five days 

 into alcohol with 10 per cent, tinctura iodi P. G-., then for eight to 

 ten into saturated solutions of potassium bichromate changed after 

 the first day, and lastly into 95 per cent, alcohol for three days in 

 the dark. 



813. Other Reagents. Osmic acid is hardly useful for specimens 

 of more than 2 or 3 mm. thickness. 



Chromic acid is rarely used alone. Its action is rapid, but uneven, 

 and causes shrinkage and brittleness. A very little (e.g. 3 to 5 drops of 

 a 1 per cent, solution to every 100 c.c. of fluid), added to bichromate 

 solutions will do no harm and quicken the hardening. 



Nitric acid, has been and still is employed in strengths of 10 to 12 per 

 cent. 



Neutral acetate of lead affords, according to KOTLAKEWSKI (Ztschr. 

 uriss. Mikr.,iv, 1887, p. 287), an excellent preservation of ganglion cells. 



Corrosive sublimate solutions either alone or mixed with other re- 

 agents (see Chapter V.), have been very often used for cytological 

 studies. 



Similarly acetic alcohol. 



MANN (op. cit.) for cell studies, puts small pieces for twenty-four hours 

 into a solution of 5 parts of potassium iodide and 25 of iodine in 100 

 parts of water, and then into 70 per cent, alcohol. 



OLMACHER ( 65) recommends his mixture. KODIS (Arch. mikr. 

 Anat., lix, 1901, p. 212) fixes tissues in a saturated solution of cyanide 



