24 PRACTICAL HISTOLOGY. 



III. NORMAL OR INDIFFERENT FLUIDS. 



Not ^infrequently living tissues or fresh tissue elements have to 

 be examined in as natural a condition as possible, and obviously, if 

 a fluid require to be added to it, the fluid must be of such a nature 

 that it will not injuriously affect the tissue or its elements. These 

 fluids are spoken of as indifferent or normal fluids. When fresh, 

 these fluids cause very slight changes in the tissues. Amongst 

 those used are 



1. Normal Saline. Dissolve 6 grams of pure sodic chloride in 

 1000 cc. water. 



2. Kronecker's Fluid. It consists of 



Distilled water . . . . . 100 cc. 



Sodic chloride . . . . . .6 gram. 



Soda .... . .06 



3. Blood Serum. The blood is allowed to clot, and the serum, 

 after a day or so, is poured away from the clot. In a laboratory 

 provided with a "centrifugal apparatus" any red blood-corpuscles 

 can be got rid of by " centrif ugalising " the serum. This fluid 

 does not keep long, and must be fresh. It has been suggested to 

 add a piece of camphor to it, but this only helps to preserve it 

 for a short time. Iodine is sometimes added to serum to form 

 iodised serum, but this is by no means an indifferent fluid 



(P- 25). 



4. Aqueous Humour. With a narrow triangular knife puncture 

 the cornea of a freshly-excised ox's eyeball and collect the aqueous 

 humour which exudes. If only a small quantity be required, it 

 may be obtained by puncturing the excised eye of a frog with a fine 

 capillary glass pipette (p. 4). 



5. Fluid of Kipart and Petit : 



Camphorated water 

 Distilled water 

 Glacial acetic acid 

 Acetate of copper 

 Chloride of copper 



It is very useful for examining animal cells. 



75 cc. 



75 

 i ,, 



o. 30 gram. 

 0.30 



IV. DISSOCIATING FLUIDS. 



These fluids dissolve or soften the cement substance or inter- 

 stitial material, e.g., of epithelium, connective tissue, and thus 

 facilitate the separation of the histological elements from each other. 

 In some cases, in isolating tissue elements, it is well not to have 



