Strong, Reviexv of the Golgi Method. 115 



pieces in less time that particular hardening most favorable to 

 the best reaction with silver nitrate. I mention, for example, 

 a case where I have obtained graduated reactions of surprising 

 fineness on pieces i 5 to 30 days after they were placed in bi- 

 chromate at a temperature of i 5° to 20° C. (in autumn), the 

 pieces having been subjected to the above treatment. 



" The injection is performed in the usual way (with a sim- 

 ple syringe or with a siphon in which the pressure is regulated 

 by the height of the vessel containing the injection fluid) either 

 through the carotid, when one wishes to limit the hardening to 

 the cerebrum and cerebellum, or through the aorta when the 

 fluid should also extend to the spinal cord. 



••It is superfluous to state that when the bichromate and 

 gelatine is injected it must be warmed so that it will remain 

 fluid. In this case it is especially important to perform the 

 operation immediately after the death of the animal, before the 

 tissues are cold. Only in this way does one secure the finest 

 and most widespread injection. 



••After the injection the nervous parts are removed from 

 their cavities, cut into pieces and brought as usual into bichro- 

 mate where they are carefully treated as dealt with above. 



'\U) Hardening in bicJiromate at a constant temperature. The 

 circumstance, pointed out several times, that the uncertainty 

 about the time at which the pieces must be brought from the 

 bichromate into the silver solution depends for the greater part 

 upon the temperature of the medium leads to the idea that the 

 best means of avoiding this inconvenience would be the em- 

 ployment of a constant temperature for the bichromate in 

 which the pieces lie. For this purpose the warm chambers used 

 in investigations upon micro-organisms seem best adapted. 



'• I have used the chamber of Wiesnegg in which I main- 

 tained a temperature of 20° to 25°. This had good success but 

 only in the direction of considerably abbreviating the period of 

 hardening in bichromate so that the reaction could be obtained 

 much sooner than formerly and in a tolerably constant period 

 of time. Thus the reaction in the warm chamber appeared 

 after 8 to 10 days and proceeded to completion up to 15 to 20 



