298 SUMMARY OF CURRENT RESEARCHES RELATING TO 



Preparations thus made are teased out in a drop of dilute glycerin, 

 or they may be sectioned after hardening in spirit. 



Macerating Fluid for Nerve-cells.* — Dr. G. C. Freeborn obtains 

 nerve-cells from the spinal cord in the following manner : — Thin slices 

 of spinal cord or cerebellum not over 1/16 in. thick are placed in fifty 

 times their volume of a 5 per cent, aqueous solution of potassium 

 chromate for 24 hours. At the end of this time the grey matter has 

 become jelly-like and transparent, and then, having been cut away from 

 the white, is placed in a long narrow tube. Mohr's burette with the 

 lower end plugged with a cork answers the purpose perfectly. The 

 burette is then tilled up to within an inch of the top with fresh mace- 

 rating fluid and a cork forced in until it comes within 1/2 in. of the 

 surface of the fluid. The burette is then inverted, and this manipulation 

 is repeated at intervals of half an hour until the bits of tissue are re- 

 duced to powder. The burette is then placed upright, and when the 

 material has all settled the fluid is poured off. The material is then 

 carefully washed with distilled water by repeated decantation, and 

 finally poured into a conical glass burette. The water is then poured 

 off and the material stained with picro- or ammonia-carmine. This, 

 which takes from 12 to 15 hours, is followed by washing in distilled 

 water and preservation in a mixture of 1 part spirit and 3 parts 

 glycerin. 



By this method cells from spinal cord and cerebellum may be 

 obtained with their processes attached down to the fourth division. 



Preparing small Intestine.f — For hardening the small intestine in 

 order to examine the epithelium, Dr. E. Heidenhain recommends a 

 saturated aqueous solution of picric acid, alcohol or chromic acid, then 

 alcohol. Sections parallel or vertical to the surface show bridges of 

 protoplasm uniting the adjacent cells. In order to render the rodlets 

 clearly visible, pieces of intestine on the cells are placed for a day in a 

 5 per cent, solution of chromate of ammonia. In the fresh villi similar 

 results can be obtained by placing pieces of the fresh mucosa in about 

 2 per cent, salt solution (1-3 per cent, according to the animal) for 

 15 to 20 minutes, then fixing in 0*1-0 -2 per cent, osmic acid, and 

 isolating the cells in order to examine the relation of the rodlets to the 

 protoplasm. To show the nodular thickenings at the lower end of the 

 rodlets, the mucosa is best hardened in alcohol and stained with 

 hsematoxylin and chromate of potash. 



In order to differentiate by staining the separate elements in the 

 villous stroma the following method is said to be very good. The pieces 

 of intestine taken from a recently killed animal are placed for 24 hours 

 in a half per cent, salt solution saturated with sublimate. They are 

 then transferred every 24 hours to alcohol of 80, 90, 97, and 100 per 

 cent. The pieces are then treated with xylol, imbedded in paraf&n, and 

 sections 0*005 to O'Ol mm. thick made; these are fixed warm on the 

 slide with 50 per cent, alcohol. It is important that the temperature 

 should not exceed 35° C. or the villous tissue will be much shrunken. 

 Staining on the slide is done with the following solution : orange 100 ccra., 

 acid fuchsin 20 ccm., methyl-green 50 com., all saturated solutions. This 



* Amer. Mon. Micr. Joiirn., ix. (1888) pp. 231-2. 



t Pliiiger's Arch, f. d. Ge^ammt. Physiol., xliii., Supplement (1888) pp. 1-103 

 (1 pL.,)- 



