"Chemists have considered the change as contributory to the production of animal heat, which opinion may, indeed, be true, though the manner in which it produces such an effect has not, as yet, been explained. Mr. Hunter, who believed that life had the power of regulating temperature, _independently of_ respiration, says nothing of that process as directly contributing to such an effect. He says: 'Breathing seems to render life to the blood, and the blood conveys it to every part of the body,' yet he believes the blood derives its vitality also from the food. I am at a loss to know what chemists now think respecting heat, whether they consider it to be a distinct species of matter, or mere motion and vibration. Among the curious revolutions which this age has produced, those of chemical opinions have a fair claim to distinction. To show which, I may add, that a lady[64], on her first marriage, was wedded to that scientific champion who first overthrew phlogiston, and established, in its stead, the empire of caloric; and after his decease, on her second nuptials, was united to the man who vainly supposed he had subverted the rule of caloric and restored the ancient but long-banished dynasty of motion and vibration. In this state of perplexity, I cannot, with prudence or probable security, advance one step further than Mr. Hunter has led me. I must believe respiration to be essential to life, and that life has the power, by its actions, of maintaining and regulating temperature[65]." CHARACTERISTIC, BOTH AS TO ILLUSTRATION AND MORAL BEARING.