1. Preliminaries 333 2. On the respiration of Nitrous Oxide by warm-blooded Animals 336 3. Effects of the respiration of Nitrous Oxide upon Animals, as compared with those produced by their immersion in Hydrogene and Water 343 4. Of the changes effected in the organisation of warm-blooded Animals, by the respiration of Nitrous Oxide 347 5. Of the respiration of mixtures of Nitrous Oxide and other Gases, by warm-blooded Animals 358 6. Recapitulation of facts relating to the respiration of Nitrous Oxide, by warm-blooded Animals 360 7. Of the respiration of Nitrous Oxide, by amphibious Animals 362 8. Effects of Solution of Nitrous Oxide on Fishes 366 9. Effects of Nitrous Oxide on Insects 370 DIVISION II. _Of the changes effected in_ NITROUS OXIDE _and other Gases, by the Respiration of Animals_. 1. Preliminaries 373 2. Absorption of Nitrous Oxide by Venous Blood 374 3. Of the changes effected in Nitrous Oxide by Respiration 388 4. Respiration of Hydrogene 400 5. Additional Observations and Experiments on the Respiration of Nitrous Oxide 411 6. Of the Respiration of Atmospheric Air 429 7. Respiration of Oxygene 439 8. Observations on the changes effected in the blood by Atmospheric Air and Oxygene 445 9. Observations on the Respiration of Nitrous Oxide 449 RESEARCH IV. _Relating to the_ EFFECTS _produced by the_ RESPIRATION _of_ NITROUS OXIDE _upon different_ INDIVIDUALS. DIVISION I. HISTORY _of the Discovery_.—EFFECTS _produced by the Respiration of different_ GASES. 1. Respirability of Nitrous Oxide 456 2. Effects of Nitrous Oxide 458 3. General Effects of Nitrous Oxide on the Health 464 4. Respiration of Hydrogene 466 5. —— of Nitrogene 467 6. Effects of Hydrocarbonate 468 7. —— of Carbonic Acid 472 8. —— of Oxygene 473 9. —— of Nitrous Gas 475 10. Most extensive action of Nitrous Oxide produces no debility 485