Abstract
As one phase of some observations on the effects of parathyroidectomy on cats, 1 a previous study 2 showed that on stimulation of the rectus abdominis muscle following thyroparathyroidectomy, more contracture usually appeared than was the case with the same muscle stimulated in the same manner in control animals. During the past months a series of experiments has been done on 20 cats in which the ionizable calcium and inorganic phosphorus of the blood were determined from 2 to 3 days after (1) aseptic transection of the spinal cord alone in the upper thoracic region and (2) when thyroparathyroidectomy was done at the same time as the spinal transection. The working power of the curarized muscle, together with the presence or absence of tetany and of contracture, was determined in the same manner as in previous experiments.
The results are given in Table I.
It appears from the table that 1. Either contracture or tetany was present in all but one case, in which the contracture occurred at the beginning of the excitation of the muscle and was merely transitory. 2. Contracture and tetany were found together in only 6 of the 20 experiments. There appears to be no necessary relationship between them. 3. Contracture did not occur when the ratio of calcium to phosphorus was less than one, except in one case (No. 9). From these and previous observations it would appear that contracture occurs infrequently when the ratio of calcium to phosphorus is less than one, and then only when the calcium is relatively low; on the other hand, contracture was observed in only one case where the concentration of phosphorus was above 8 mg. per 100 cc. serum. (No. 6.)
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