428 CHAPTER XXXII. 



dropping formic acid slowly into solution of acetate of lead. 

 White crystals of formate of lead are abundantly formed ; 

 the mother liquor is filtered off, and the crystals are dis- 

 solved to saturation in water. The solution is mixed with 

 an equal volume of 10 per cent, formol solution ; pieces of 

 brain or spinal cord are put into the mixture for five days, 

 and are then brought direct into a mixture of equal parts of 

 10 per cent, formol solution and hydric sulphide solution. 

 After five days therein they are passed through successive 

 alcohols, imbedded in celloidin, cut, and the sections mounted 

 in xylol-balsam under a cover. They seem to be quite per- 

 manent. Nerve cells as well as nerve fibres are impregnated, 

 and it is the elements themselves that are impregnated, and 

 not lacuna? around them, as appears to be the case with the 

 Grolgi impregnation. The impregnation is a very complete 

 one. 



CORNING (Anat. Anz., xvii, 1900, p. 108) hardens the 

 tissues with 10 per cent, formol before bringing them into 

 the formol -formate mixture, and so obtains better results. 

 He obtains his formate of lead direct from MERCK (Plwn.bum 

 formicicum). He thinks the celloidin imbedding injurious, 

 and prefers to cut without imbedding. He prefers to clear 

 sections with clove oil. The method appears to him par- 

 ticularly useful for the medulla oblongata, with which the 

 Grolgi method does not succeed. It appears likely to be 

 very useful in pathological researches, and also for the 

 naked -eye differentiation of white and grey matter, as well 

 as for the other purposes for which the Golgi method is 

 generally employed. Other details loc. cit. 



774. ROBERTSON^ Platinum Impregnation. See Journ. Roy. Mic. 

 Soc., 1899, p. 665. 



775. WEIGERT'S Specific Neuroglia Stain (WEIGEKT'S Beitr. 

 zur Kenntnisx der normalen men* ch lichen Neuroglia, Frank - 

 furt-a-M., 1895 ; quoted from Neurol. Centralb., 1895, xxiii, 

 p. 1146). Pieces of tissue of not more than half a centi- 

 metre in thickness are put for at least four days into " 10 per 

 cent, solution of formol." They are then mordanted for four 

 or five days in an incubating stove (or for at least eight days 

 at the temperature of the laboratory) in a solution containing 



