176 PRACTICAL HISTOLOGY. 



hot, and the filtrate is allowed to trickle into 6oCC 

 rectified spirit. Slices of cartilage are allowed to remain in 

 the fluid from 24 to 48 hours. They are then washed in 

 water, and mounted in glycerine. The nuclei and nucleoli 

 of the cells are brightly coloured, the cartilage matrix 

 faintly so. He also recommends its use in studying intra- 

 cartilaginous ossification. It stains tissues hardened in 

 chromic acid. 



327. Silver Nitrate. His, but more particularly 

 Recklinghausen, introduced this substance into histology. 

 It is of great value for staining the epithelium of serous 

 membranes, lymphatics, and blood-vessels. It also stains 

 the matrix of connective tissue and of cartilage, and often 

 the nuclei of cells. In addition to staining, it fixes albu- 

 minous matter, and is thus valuable by facilitating the 

 preservation of delicate tissues, e.g., adenoid tissue of 

 lymphatic gland, epithelium of intestine. A solution of the 

 salt is commonly used, but the solid form is also sometimes 

 employed for the cornea. 



328. The ordinary silver process. A \ per cent solution 

 in distilled water is usually employed, but somewhat weaker 

 solutions may also be used. In silvering a tissue e.g., the 

 mesentery of the frog, or omentum of guinea-pig or cat dip 

 it two or three times into distilled water to remove sodium 

 chloride. Place it in the silver solution from one to three 

 minutes. Remove the superfluous silver by washing in 

 distilled water. Place the washed tissue in glycerine or in 

 distilled water, but glycerine is better, and expose it to 

 diffuse daylight until it becomes slightly brown. Mount in 

 glycerine, or in glycerine jelly. 



By exposure to light the silver salt is reduced, and the 

 tissues are thereby blackened. If the immersion of the 

 tissue in the silver solution be of very brief duration, only 

 the outlines of the epithelial cells are blackened. The 

 cells appear to be united by a colourless " cement/' which 

 readily reduces the silver salt when acted on by light. If 

 the silver act for some time longer, the nucleus and general 

 substance of the epithelial cells is blackened, also the 

 nuclei of fat cells, connective tissue corpuscles, etc. 





