CHAPTER XXXIL 425 



fibres, large and small, 2a or 6a. For buds of Held and Auerbach 

 and for fine plexuses, 4a, 3a, A, or 5a. 



(8) Ganglia of invertebrates. For the medicinal leech (not for 

 other leeches), la, A. For Hcemopis, Aulostomum, Pontobdella and 

 Glossiphonia, 2a or, better, 3a, with not more than 2 to 5 drops of 

 ammonia and 3 per cent, silver nitrate, stoving three or three and a 

 half days. For further details see SANCHEZ, Trab. Lab. Invest. .BioL, 

 Madrid, vii, 1909, pp. 4247. 



Lumbricus is generally refractory to Cajal's methods. BOULE 

 (Le Nevraxe, x, 1908, p. 15) obtained good impregnations by acidi- 

 fying the fixatives. He takes : (a) 25 per cent, formol with 5 per cent, 

 of acetic acid ; or (b) the same with -5 per cent, of ammonia ; 

 or (c) 100 c.c. of alcohol, 25 c.c. of formol, 5 c.c. of acetic acid, and 

 0-5 c.c. of ammonia. For the impregnation he uses. 3 per cent, 

 silver nitrate with 15 per cent, of alcohol, and reduces in the usual 

 hydroquinone-formol solution, with the addition of 15 c.c. of alcohol. 

 These results are confirmed by KOWALSKI (La Cellule, xxv, 1909, 

 p. 292, and by SCHUTZ (Anat. Anz., xlii, 1912, p. 262). Kowalski 

 gets impregnations also by simply starving worms for several days, 

 or exposing them to cold (- - 5 C.) for a quarter of an hour. 



(9) Regenerating nerve tissue. For nerves operated a month 

 or more previously, Formula 2a or 3a, with not more than 3 drops 

 of ammonia, will stain equally the old and the new fibres ; for nerves 

 operated not more than two to ten days previously, Formulae 3a 

 with 4 to 6 drops of ammonia, 5a with pyridine, and 4a, also some- 

 times 6a ; for regeneration in cord, cerebrum, and cerebellum, 

 3a with 3 drops of ammonia, or 5a, or pure alcohol. 



839. Modifications of EAMON Y CAJAL'S Methods. DA FANO (Ziegler's 

 Beitr., xliv, 1908, p. 495) recommends using solutions of silver nitrate 

 and hydro quinone in 1 : 10,000 gelatin in order to obtain a deeper and 

 sharper impregnation. 



KAT6 (Folia neurobiol, ii, 1908) fixes in 10 to 15 per cent, formol, and 

 silvers for one to five days at 35 C. in 5 per cent, argentamin to which 

 3 per cent, of silver nitrate has been added in such a way as to have an 

 impregnating fluid with a little argentamin in excess ; or argentamin 

 eight to ten parts, with 3 per cent, potassium bichromate thirty parts 

 and distilled water 100 parts. For the reduction he uses 10 per cent, 

 formol with 1 per cent, hydroquinone. 



PUSATERI (see AMATO, Virchow's Arch., clxxxv, 1908, p. 547) fixes 

 for three to six days at 35 to 38 C. in a mixture of 45 c.c. of tachiol 

 (10 per cent, silver fluoride) and 155 of distilled water. 



BESTA (Eiv. pat. nerv. ment. Firenze, xv, 1910, p. 333) fixes for forty- 

 eight hours in alcohol with 5 per cent, nitric acid, neutralised in alcohol 

 with ammonia. 



