ETC. 391 



living tissues may be examined without undergoing the 

 changes caused by pure water. 

 Preparation. — The strong solution (twenty per cent.) may 

 be made by dissolving twenty grams of common table salt 

 in eighty cubic centimetres of distilled water, and from 

 this weaker solutions may be prepared. The " normal " 

 (three-quarter per cent.) salt solution is made by adding 

 seven and a half grams of salt to one litre of distilled water. 



37. Schulse's Macerating Mixture. 



Use. — Separates the constituent elements of vegetable tis- 

 sues by dissolving the middle lamella. Used cold the 

 mixture gives better results, but works more slowly than 

 when warmed. Do not expose the microscope to the 

 fumes given off. 



Preparation. — Dissolve one gram of potassium chlorate in 

 fifty cubic centimetres of nitric acid. 



38. Sea-water {artificial). 



The following formula gives an artificial sea -water in 

 which starfishes, lobsters, etc., may be kept alive for 

 some time : 



Water . . . 3 to 4 litres 



Sodium chloride (salt) 81 grams 



Magnesium sulphate 7 " 



Magnesium chloride 10 " 



Potassium chloride 2 



This water should frequently be aerated by pouring from 

 a height into the tank. 



39. Silver Nitrate. 



Use. — A stain for fibrous tissues. The tissue to be stained 

 is spread upon the slide in a drop of the solution, and 

 exposed to the sunlight until a brown color is assumed. 

 The preparation is then washed in distilled water. 



Preparation. — Dissolve one -half gram of the crystals of 

 silver nitrate in one hundred cubic centimetres of distilled 

 water. Keep in the dark in a glass-stoppered bottle. 



