THE INORGANIC KINGDOM.
103
\b). On animals generally. —It is usually asserted that all animalsrequire the influence of oxygen, or rather of air, to enable them to exist:but this assertion cannot be proved in the case of some of the loweranimals. Thus intestinal worms seem to dispense with respiration(Muller’s Physiology, p. 295). Some animals which respire have noorgans specially devoted to this function ; in these the cutaneous surfaceeffects respiration; as in the Polypifera. In the Infusoria the respiratoryorgans are delicate cilia. Many animals have branchiae or gills forrespiration, as some Mollusca , some Annelida , and fishes. Leechesrespire by subcutaneous sacs which open externally. The respiratoryorgans of insects are ramifying tracheae. Lastly, the higher classes ofanimals respire by means of lungs. Whenever respiration is effected aportion of oxygen disappears, while a quantity of carbonic acid, nearlyequal in volume to the oxygen consumed, is produced.
The continued respiration of oxygen gas is injurious, and even fatal toanimal life : this has been observed by all experimenters. Animals livelonger in a given volume of oxygen than in the same quantity of atmo-spheric air, but the continued employment of it causes death. Mr.11 rough ton confined rabbits, guinea-pigs, and sparrows, in glass jars con-taining oxygen, and inverted over water. At first they suffered no incon-venience, but in about an hour their breathing became hurried, and thecirculation accelerated. This state of excitement was followed by one ofdebility; the respirations became feeble, and were more slowly performed;loss of sensibility and of the power of voluntary motion supervened, till theonly remaining visible action was a slight one of the diaphragm, oc-curring at distant intervals. On opening the body, the blood (bothvenous and arterial) was found to be of a bright scarlet hue; it was thin,and rapidly coagulated. The gas in which animals had thus been con-fined till they died, retained its power of rekindling a blown-out taper,and of sustaining, for a time, the life of another animal introduced intoit; and Mr. Broughton hence deduced the inference that it does notcontain so great an excess of carbonic acid as the gas left when animalshave perished by confinement in atmospheric air, and lie considered thetrain of symptoms induced by the respiration of pure oxygen gas asanalogous to those which follow tlie absorption of certain poisons into thesystem ( Medical Gazette, vol. iii. p. 775). Injected into the pleura, oxygengas is very quickly absorbed, without producing inflammation. Cau-tiously injected into the veins of dogs, it has no sensible effect on thesystem {Nysten, Recherches de Physiologie, p. 60).
(i c .) Effects on man. —If pure oxygen be inspired a few times it doesnot produce any remarkable phenomena; though some have ascribedvarious effects to it, such as agreeable lightness in the chest, exhilaration,increased frequency of pulse, a sensation of warmth in the chest, gentleperspiration, and an inflammatory state of system. But several of theseresults arise probably from mental influence, others from the mode ofinhaling the gas, and perhaps some might depend on the employment ofimpure oxygen.
Uses. —Oxygen gas was formerly employed in medicine in certaindiseases supposed to depend on a deficiency of oxygen in the system;and the beneficial results obtained by the use of acids (especially thenitric acid) of the oxides of mercury, chlorate of potash, vegetable food,&c. were relerrcd to the oxygen which these substances contained, and