Abstract
Two methods of approach have been used by investigators for the extirpation of the hypophysis of the rat. The parapharyngeal approach proposed by Smith 1 which has been modified by several investigators is the one most commonly used. The second method, suggested by Koyama, 2 is through the ear. The temporal approach used successfully on dogs by Dandy and Reichert 3 has not been, to our knowledge, used on rats. This method is particularly adapted for operating on rats, (1) because the sella turcica is shallow and a satisfactory approach can be obtained from the side; (2) the rat is very resistant to infection; (3) the anterior and the posterior lobe of the hypophysis in the rat can be removed separately by this approach. This cannot be done with dogs. (4) The lobes can be removed intact and may be used for microscopic examination; (5) the operation can be carried out on very young animals.
The work of Weed and McKibben 4 on the experimental alteration of the brain bulk has been useful in this operation. The decrease in the brain bulk of rats given intravenous injection of hypertonic sodium chloride solution is very striking.
Under light ether anesthesia sufficient hypertonic salt solution is injected intravenously in order to obtain the maximum amount of brain shrinkage. We have been using 400 mg. of sodium chloride per kilo of body weight. This is slightly more than the amount used by Weed and McKibben on cats and by Dandy and Reichert on dogs. In rats weighing over 100 gm., the sodium chloride was injected very slowly into the jugular vein in a 20% solution. Rats weighing less than 100 gm. were given sodium chloride in a 5% solution.
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