MS 22.21-MS 23.0 



METAL STAINS 



539 



22.21 Ziehen 1891 15058, 10 :65 



REAGENTS REQiiREo: A. MS 22.1 Ziclieii 1891; B. ADS 12.2 Lugol 1905 20, water 80 

 method: [fresh tissues] —> A, 1-0 months, till copper red — + [sections by freezing tech- 

 nique] -^ B, till differentiated — > balsam, via usual reagents 

 RECOMMENDED FOR: axis Cylinders and dendrites. 



22.22 NEUROGLIA 



22.22 Cajal 1916 21344, 14:155 



reagents required: A. AMS 11.1 Cajal 1913; B. MS 22.1 Cajal 1916; C. AMS 24.1 



Cajal 1913 

 method: [fresh tissue] — > ^, 2 to 10 days — > wash -^ [sections by freezing technique] — > 



rinse -^ 5, 4 to 6 hrs. -^ wash — > C, 6 to 10 mins. -^ wash, 40% ale. -^ balsam, via 



usual reagents 



22.22 Raileanu 1930 6630, 104 :285 



reagents required: A. 6% neutralized formaldehyde; B. AMS 11.1 Raileanu 1930; 



C. MS 22.1 Raileanu 1930; D. AMS 24.1 Raileanu 1930 

 method: [fresh tissue] -^ A, 24 hrs. at 37°C. — > [sections by freezing technique] —> B, 



24 to 48 hrs. -^ wash — > C, in dark, 4 to 7 hrs., till deep violet -^ wash — > D, 15 mins. 



— » wash, 30 mins., 50% ale. -^ balsam, via usual reagents 



23 METHODS USING GOLD IN OTHER COMBINATIONS 



23.0 Typical Example 



Demonstration of the nervous 



elements in spinal cord by 



the method of Gerlach 



1872 



It is a pity that this method should 

 have become obsolete and that it is today 

 cited in so few textbooks. The method is 

 simple and certain, hence it is suitable 

 for class demonstration, and it shares with 

 the method of Ranvier, already described, 

 the distinction of being the only gold tech- 

 nique that may reasonably be so em- 

 ployed. It is not suitable for original 

 research, since the structures which it 

 displays are already well known, but it 

 cannot be surpassed for a method of pre- 

 paring demonstration material. 



Only four solutions are required, all of 

 which are stable indefinitely. These solu- 

 tions are: first, a 1% solution of ammo- 

 nium dichromate, which must, of course, 

 be prepared from a reagent of analytical 

 grade; second, a 0.01% solution of gold 

 chloride; third, 0.5% hydrochloric acid; 

 and fourth, 0.1% hydrochloric acid in 

 60% alcohol. These solutions, with the 

 exception of the gold, should be available 

 in relatively large volumes. In the descrip- 

 tion which follows it will be presumed that 

 the method is being utiUzed for the in- 



struction of a class in an ele mentary tech- 

 nique of gold staining. 



The instructor should first secure short 

 lengths of spinal cord from a freshly killed 

 mammal. The technique works equally 

 well on the spinal cords of fish and am- 

 phibia, but these are in general too small 

 for convenient handling by a class. The 

 cord should be cut into approximately 

 one-inch lengths and placed in a large 

 volume of the ammonium dichromate so- 

 lution in a stoppered bottle. It is a matter 

 of convenience that this bottle should 

 have about a one-inch layer of fat-free 

 absorbent cotton or of glass fiber on the 

 bottom, to prevent the distortion of the 

 spinal cord through pressure against the 

 glass. The period of fi.xation should be 

 from two to three weeks and is not critical. 

 At the beginning of the week in which the 

 class is to be held, the lengths of spinal 

 cord should be removed from the reagent 

 and washed in running distilled water for 

 at least 24 hours. They may then be left 

 in a bottle of triple-distilled water until 

 required for class purposes. 



A freezing microtome can be used to cut 

 sections for issue to the class, but the 

 shape and hardness of the spinal cord 

 makes it convenient for freehand section- 

 ing, either between layers of the pith, or 

 by any other method customarily used in 

 the class in question. These freehand sec- 



