AND HOW TO USE IT. 237 



Saturated Aqueous Solution of Baric Hydrate requires about 

 twenty-four hours to act on the fibrillae of tendon. 



Caustic Potash. — Dissolve 40 grammes of potash in 100 cc. 

 of water ; it isolates muscle-cells in from twenty to thirty minutes. 



Ten per cent, solution of Common Salt is useful for dis- 

 solving the cement of white fibrous tissue. It takes several days 

 to act. It is very useful also for showing the fibrillas of the matrix 

 of the bone. 



Nitric Acid and Glycerine. — Mix i part of strong nitric acid 

 containing nitrous acid, with 3 parts of water, and i part of 

 glycerine. The object is placed in this mixture for two or three 

 days, and then in water. It is specially useful for isolating nerve- 

 structures and lens-fibres of the eye. 



Teasing 

 Is done with needles, mounted in some kind of handles. Cut a 

 very small piece of the tissue, and place it on a slide in a small 

 drop of the fluid in which it is to be mounted — generally glycerine. 

 Fix one end of the tissue with a strong needle, and tear it with the 

 other needle in the direction parallel with the fibres. Some 

 tissues cannot be so separated, so they must be broken up into 

 minute pieces. Examine from time to time with a lens or a 

 dissecting microscope. If it be a coloured object, a small piece of 

 white bibulous paper should be used for a background ; if un- 

 coloured, a dark surface. 



Digestion 

 As a histological method has been recently employed by Kiihne 

 for investigating the structure of nerves, and by De Burgh Birch in 

 studying the composition of the matrix of bone. Either artificial, 

 gastric, or pancreatic juice may be employed. Artificial pancre- 

 atic, i.c.^ Trypsin digestion. — Use either an aqueous or glycerine 

 extract of the pancreas. The latter I prefer, which is made as 

 follows'' : — The pancreas of a dog is chopped up and dehydrated 

 with absolute alcohol for twenty-four hours. The alcohol is 

 removed, and sufficient pure glycerine is added to cover the 



* Von Wittich's method. 



