SECTION TWO 



6. Repeat 3, 4 and 5 until the sections turn brown. 



7. Transfer the sections to solution C. 



8. Differentiate quickly in solution D (formic acid 25%). 



9. Wash well in distilled water. 



10. Dehydrate in 95% and absolute alcohols. 



11. Clear in xylol and mount. 



Results: 



The method shows up the dendrites of the cells, the neuroglia 

 cells, the course of the nerve fibres and of the blood vessels ; the 

 tigroid substance and sometimes the intracellular neurofibrils, and 

 it gives excellent results for a general study of nerve centres and 

 their connections, demonstrating the most delicate nerve exten- 

 sions. 



The different structures and the cellular elements assume a 

 brown tint. 



Notes: 



[a) The author (Novelli) observes that although the methods 

 for the microscopic study of nervous tissue are very numerous, 

 for the most part they are modifications or variations of the few 

 fundamental procedures, i.e. the Nissl method, Golgi silver im- 

 pregnation, the so-called " photographic " methods of Cajal, the 

 Bielschowsky ammoniacal silver impregnation method, and, 

 finally, the Weigert iron haematoxylin method. Impregnation 

 methods in particular are not easy to perform; they are lengthy 

 and not always successful. 



[b) Novelli's method, described above, however, differs from 

 all other impregnation methods known at the present time in 

 that a completely different reagent is employed, the procedure is 

 rapid and easy to carry out. It is stated in the original paper that 

 the method has proved to be successful on all occasions. 



{c) It is stated that solution B (potassium permanganate) must 

 be made up fresh each time; this, however, should not be neces- 

 sary. Provided the solution is kept free from extraneous matter 

 and in a well-closed bottle, stored in a cool place away from 

 strong light, it should be good for a few days at the very least. 



Reference: Novelli, A. (1952). 



421 



