DISSOCIATING FLUIDS. 2$ 



too much fluid in proportion to the morrel of tissue, else hardening 

 is more apt to take place. 



1. Strong Iodised Serum. A strong solution should be kept, 

 which may be diluted as required. To the amniotic fluid of a cow 

 or to blood-serum add crystals of iodine, and keep it in a stoppered 

 bottle. Shake it frequently. At first very little iodine is dissolved, 

 but after a time (15-20 days) the solution becomes much stronger, 

 i.r., it becomes of a deep-brown tint. 



For dissociating a tissue, a weak iodised serum is used. A 

 little of the strong fluid is added to fresh serum until the latter has 

 a light-brown colour. If an object be placed in the dilute iodised 

 scrum and the brown colour fades, more of the strong solution 

 must be added. In using this fluid, take a very small piece of 

 tissue, the size of half a pea or less, and place it in 5 cc. of the 

 fluid in a glass-stoppered bottle. After a day or two it may be 

 dissociated with needles, but the brown tint must be maintained ; 

 more strong fluid must be added if putrefaction is to be pre- 

 vented. 



2. Dilute Alcohol (Ranvier's Alcool au t'wrs). This fluid, 

 devised by Ranvier, and sometimes called "one-third alcohol," is 

 of the greatest possible service, and is one of the best dissociating 

 fluids we possess. Mix i part of 96 per cent, alcohol with 2 parts 

 of distilled water. It dissociates epithelial and other tissues in 

 24-36 hours. Use a small quantity of the fluid in proportion to 

 the tissue. 



3. Chromic Acid. One gram in 1000 of water. This requires 

 two days to a week, according to the tissue placed in it. 



4. Potassic Bichromate. Two parts in 1000 of water, >., .2 

 per cent. It is very useful for dissociating epithelium and the 

 nerve-cells of the spinal cord. It does so in 2-3 days. 



5. Ammonium Chromate (5 per cent.). It is used for disso- 

 ciating the " rodded " cells of the renal tubules, cells of salivary 

 glands, Purkinje's fibres of the heart, &c. It acts in 24-36 hours, 

 and the chromate must be well washed out of the tissues if they 

 arc to be preserved. 



G. Caustic Potash. Thirty to 35 parts in 100 of water. It acts 

 in 20-30 minutes, rapidly destroying connective tissue. Water must 

 not be added to the dissociated tissue, else the tissues are rapidly 

 dissolved. It is used for isolating the fibres of smooth muscle, or 

 heart-fibres. Examine the dissociated tissues in the dissociating 

 fluid. As a rule, tissues so dissociated cannot be preserved, but 

 there are certain exceptions. 



7. Dilute Osmic Acid (.1 per cent.). It acts in 24-48 hours 

 according to circumstances, and is well suited for cells containing 

 fat globules. 

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