THE INFLUENCE OF MUSCULAR RIGIDITY ON THE CARBON DIOXIDE OUTPUT OF DECEREBRATE CATS

Abstract

1. In decerebrate animals the muscles become rigid. This rigidity differs from ordinary tetanus as it does not readily become fatigued. Previous observers have suggested that the metabolism underlying the rigidity is different from that which accompanies ordinary contraction.2. The carbon dioxide output has been measured in the cat after decerebration, and also after other treatment of the decerebrate preparation.3. The temperature coefficient for carbon dioxide output is about 2·5±0·2.4. By applying suitable corrections for the internal temperature and weight of the preparation, a fairly uniform carbon dioxide output can be calculated. The formula is Carbon dioxide output in grms. x (2·5)40−t/10/3√weight. = respiratory ratio.5. The average of twenty‐three experiments gives a respiratory ratio of 1·705±0·026, and the median is 1·695, showing that the distribution is a portion of a normal curve.6. Slight muscular movements increase the carbon dioxide output to an average of 1·930±0·054 for ten experiments. This is 0·225 above the ordinary decerebrate preparation, and the probable error of the difference is 0·060.7. Abolition of decerebrate rigidity by curare does not cause any significant reduction in the carbon dioxide output, the average for eleven experiments being 1·669±0·047. This is less than the average of the ordinary decerebrate preparation by 0·036, and the probable error of the difference is 0·054.8. Cutting the nerves to all four of the limbs abolishes the rigidity in the limbs, but does not diminish the carbon dioxide output.9. By excluding the muscles of the limbs, the carbon dioxide output of these muscles was found to be of the same order as that of resting muscles.10. It is therefore evident that the decerebrate rigidity differs from tetanus in that it does not cause an increase in carbon dioxide output.11. Decapitation and cutting of the spinal cord both diminish the carbon dioxide output. This, as shown above, cannot be due to the abolition of the rigidity. It seems possible that the reduction is due to general circulatory disturbance, but decreasing the blood‐pressure by cutting the splanchnic nerves does not appear to produce so great a diminution as that which occurs as the result of cutting the spinal cord.12. Removal of all the abdominal viscera diminishes the carbon dioxide output to 1·250±0·066 as the average of three experiments. This is 0·455 below the average of the ordinary decerebrate preparation, and the probable error of the difference is 0·071.13. It appears that a large amount of the carbon dioxide output is furnished by some portion of the body other than abdominal organs or skeletal muscles.