Appendix B: Some Standard Reagents and Their Uses 187 



III. NORMAL OR INDIFFERENT FLUIDS 



(For fresh tissues) 



70. Aqueous Humor. Obtained by puncturing the cornea of a 

 freshly excised beefs eye. A small amount may readily be 

 obtained by means of a capillary pipette from the eye of a freshly 

 killed frog. 



71. Blood Serum. Blood is allowed to clot and after 24 hours 

 the serum is poured off. If necessary it may be further freed 

 of blood cells by means of a centrifuge. The serum will keep for 

 only a day or two. Schnitzels iodized serum made by saturating 

 blood serum with iodine is sometimes classed as an indifferent 

 fluid, but it is really a dissociating fluid. 



72. Fluid of Ripart and Petit.- 



Carnphorated water , . . 75.0 c.c. 



Acetate of copper 0.3 gram 



Chloride of copper 0.3 gram 



Distilled water 75.0 c.c. 



Glacial acetic acid 1.0 c.c. 



After the solution becomes clear (a few hours) it should be 

 filtered. It is especially useful for examining fresh animal cells. 

 Methyl green is an excellent stain to follow this fixing fluid. 



73. Kronecker's Fluid.- 



Distilled water 100.00 c.c. 



Sodium chloride 0.60 gram 



Sodium carbonate 0.06 gram 



74. Normal Saline. A 0.7 per cent, solution of sodium chloride 

 in distilled water. 



IV. DISSOCIATING FLUIDS 



75. Bichromate of Potassium. A 0.2 per cent, aqueous solution 

 is commonly used. Nerve cells of the spinal cord and also vari- 

 ous epithelia dissociate well in it (2 to 3 days). 



76. Caustic Potash. A solution of 35 parts in 100 parts of 

 water is often used for isolating fibers of smooth muscle or heart 

 fibers. It acts by rapidly destroying the connective tissue (20 to 

 30 minutes). Examination of the tissue is made by mounting it 

 in the dissociating fluid. If water is added the tissue will be 

 destroyed. Usually only temporary preparations are made in 



