AND HOW TO USE IT. , 233 



brain and epidermis, its action is quite superficial. Objects on 

 which this has been used should be carefully washed and mounted 

 in glycerine. 



Gold Chloride selects and stains certain tissues, principally 

 nervous ; it also brings out the cells of fibrous connective tissue, 

 cartilage, and cornea. Remove the tissue, and place it imme- 

 diately in 5 per cent, solution of gold chloride for half-an-hour to 

 an hour ; it should then be removed to distilled water for about 

 twelve hours, and afterwards exposed to light in a saturated solu- 

 tion of tartaric acid until it sinks. Formic acid may be used in 

 place of tartaric acid. 



Method of preparing Gold Solution.— The gold is sold in 

 small glass tubes, each containing 15 grains of chloride, equal to 

 7 grains of pure gold. Take one of these tubes and file a ring 

 round it, above the bulb ; it can then be easily divided into two 

 parts. Empty the gold chloride into a six-ounce bottle, and 

 wash out any particles that remain with distilled water, and fill 

 up the bottle. This will make less than | per cent, solution, but 

 answers very well, and should be preserved in a dark bottle 

 similar to nitrate of silver. Mount the preparation, if it is thin 

 like a rat's tail, in glycerine. (For further particulars see " Staining 

 with Gold Chloride," Journal of Microscopy^ Vol. IV., p. 244.) 



Lime-water. — After maceration for six or eight days, connective 

 tissue and tendons may be separated into fibrillas by needles. 



Baryta-water acts similarly to the above, in from four to six 

 hours. The swelling is greater, and the transparency more con- 

 siderable. In both cases before the appUcation the tissue is to be 

 washed with distilled water, or, what is better, distilled water with 

 a drop of acetic acid. 



Drying Process is especially useful for skin, tendons, walls of 

 vessels, lungs (even injected), muscles, epidermis, crystalline lens, 

 umbilical cord, intestine ; the latter we have injected and then 

 dried with great success. The dried pieces can be kept in a box, 

 with the addition of a piece of camphor, and constitute excellent 

 material for many histological demonstrations. Dry on a board 

 or a piece of cork ; to avoid wrinkUng they may be stretched and 



