58 THEMICROSCOPIST. 



" The A 1 fluid is too strong for most purposes, and is only 

 to be employed where great astringency is required to give 

 form and support to delicate structures. 



" The A 2 fluid may be very extensively used, and is best 

 adapted for permanent preparations; but neither of these fluids 

 should be used in the preservation of animals possessing any 

 carbonate of lime (all the Mollusca), as the alum becomes de- 

 composed, and the sulphate of lime is formed and precipitated, 

 and the animal spoiled. For such use the 



B fluid, specific gravity 1-100. 



Bay salt, 8 ounces, 

 Corrosive sublimate, 2 grains, 

 Water, 1 quart. 



"Marine animals require a stronger fluid of this kind, viz., 

 specific gravity 1-148, which is made by adding more salt 

 (about 2 ounces) to the above. 



"The corrosive sublimate is used to prevent vegetation grow- 

 ing in the fluid, and no greater quantity should be used than 

 2 grains per quart of fluid; but, as it coagulates albumen, it 

 must be left out when ova are to be preserved, or when it is 

 desired to maintain the transparency of certain tissues." 



MOUNTING IN FLUID. 'The most minute structures, such as 

 the vessels of plants, and the muscular and other tissues of 

 animals, requiring in all cases high powers for their proper ex- 

 hibition, must of necessity be preserved in very thin cells with 

 a small amount of fluid. 



On a slip of glass, 3 inches by 1, cleaned by a solution of 

 caustic potash to remove all grease, lay a drop of the fluid ; 

 put the object in this arid spread it out with the point of a 

 needle, &c. Select a thin and flat glass cover, clear it likewise 

 from grease, &c., touch its edges with cement, and drop it 

 gently over the object. Press it lightly, to exclude the excess 



