[205] I did not attempt to experiment upon animals, because they die nearly in equal times in non-respirable gases, and gases incapable of supporting life and possessed of no action on the venous blood.
[206] Dr. Beddoes has given some account of this experiment, in his Notice of some observations made at the Medical Pneumatic Institution. It was noticed in Mr. Nicholson’s Phil. Journal for May 1799.
[207] Mild physical pleasure is perhaps always destructive to action. Almost all our powerful voluntary actions, arise either from hope, fear, or desire; and the most powerful from desire, which is an emotion produced by the coalescence of hope or ideal pleasure with physical pain.
[208] Pure hydrogene has been often respired by different Philosophers, particularly by Scheele, Fontana, and the adventurous and unfortunate Rosier.
[209] I believe it had never been breathed before by any individual, in a state so little diluted.
[210] I ought to observe, that between eight and ten, I took by the advice of Dr. Beddoes, two or three doses of diluted nitric acid.
[211] By whatever cause the exhaustion of organs is produced, pain is almost uniformly connected with their returning health. Pain is rarely ever perceived in limbs debilitated by fatigue till after they have been for some hours at rest. Pain is uniformly connected with the recovery from the debility induced by typhus, often with the recovery from that produced by the stimulation of opium and alcohol.
[212] Carbonic acid is produced in this way in a high state of purity, and with great readiness.
[213] Carbonic acid possesses no action on arterial blood. Hence perhaps, its slight effects when breathed mingled with large quantities of common air. Its effects are very marked upon venous blood! If it were thrown forcibly into the lungs of animals, the momentary application of it to the pulmonary venous blood would probably destroy life.
[214] In a conversation with Mr. Watt, relating to the powers of gases, that excellent philosopher told me he had for some time entertained a suspicion, that the effects attributed to oxygene produced from manganese by heat, in some measure depended upon nitrous acid suspended in the gas, formed during ignition by the union of some of the oxygene of the manganese with nitrogene likewise condensed in it.