CHAPTER XXXIV. 455 



any one of them for more than a very short distance. Golgi's 

 method selects from among the elements present a small number 

 which it stains with great intensity and very completely ; that is 

 to say, they are very clearly separated throughout a great distance 

 from those elements which have remained uncoloured. 



Axis-cylinders are generally impregnated only as long as they 

 are non-medullated. In the adult the method stains nerve cells and 

 their processes so far as these are not myelinated ; but if it be 

 wished to impregnate throughout a great length the axis-cylinders, 

 their arborisations and collaterals, the method is best applied to 

 embryos or new-born animals, at a time when nerve fibres have not 

 yet become surrounded by their myelin sheath. 



Nervous tissue is not the only thing that is impregnated in these 

 preparations : neuroglia, connective tissue, fibrils, etc., also become 

 stained, and the method has been applied with success to the study 

 of bile capillaries, gland ducts, and the like. Both on account of 

 this peculiarity and of the fact that the impregnation may be 

 limited sometimes to certain elements, sometimes to others, care 

 should be exercised in the interpretation of the results obtained. 

 A further source of possible error is found in the formation of 

 precipitates which may, up to a point, simulate dendrites and 

 other structures. 



The Golgi methods have been applied with success, also, to tissues 

 of invertebrates insects, Lumbricus, Tiibifex, Helix, Limax, 

 Distomum, Astacus, Actinida, etc. 



The methods have been described at length by GOLGI in Biv. Sperim, 

 Freniatr. I, 1875 ; Arch. p. le Sc. Med., iii, 1878 ; Arch. Ital. Biol., vii. 

 1886, p. 15 et seq. ; Opera Omnia, Milano, I and II, 1903, and many 

 other publications. A valuable account of the rapid process has been 

 given by v. LENHOSSK in his Feinere Bau d. Nervensy stems, 2nd ed., 1895, 

 and of both Golgi's methods and their modifications by Kallius in the 

 art. " Golgische Methode," in the Enzyk. d. mik. Technik I, 1910. 



881. GOLGI'S Bichromate and Nitrate of Silver Method. SLOW 

 PROCESS. (a) The Hardening. The tissues must be hardened in a 

 bichromate solution. Either pure potassium bichromate may 

 be employed or Miiller's fluid. (The reaction can be obtained 

 with Erlicki's fluid, but this is not to be recommended.) The 

 normal practice is to use potassium bichromate, beginning with 

 a strength of 2 per cent, and changing this frequently for fresh 

 solutions of gradually increasing strength 2J, 3, 4, and 5 per cent. 

 The tissue should be as fresh as possible, though satisfactory results 

 may sometimes be obtained from human material colfected at the 



