Friday, January 18, 2013

1750-1870: Air is defined

Stephen Hales (1677-1761)
So by the 1750s it was well known that air was more than just an element, that it was composed of certain gases.

In 1553, Michael Servetus was the first to speculate that it was the lungs that caused dark blood to become bright red, and not the heart.

In 1640, William Harvey was the first to describe the systemic circulation of the blood through the vessels of the body.

In 1668, John Mayow was the first to speculate that the purpose of the lungs was not to cool the heart, but for the exchange of gases.  He believed a substance in the air -- nitro-aerial gas -- was inhaled into the lungs, and when it entered the blood stream the blood turned from a dark color to a bright red.  This, he speculated, was why venous blood was dark and arterial blood red.

He also speculated that a vapor produced by the blood was exhaled by the lungs. He did not know that nitro-aerial gas was oxygen, and he did not know that the substance produced by the blood and exhaled by the lungs was carbon dioxide. He may have made thes discoveries had he not died at the young age of 35, before any of his works were published.

So, by 1750, investigators had determined that one of these gases was fixed air that was exhaled by the lungs, and the other was a vapor that was inhaled by the lungs.  In the next 50 years the composition of air, and the purpose of respiration, would be well known.

Stephen Hales performed experiments on air and respiration, and he proved that there is no circulatory system in trees like there is in humans and animals.  (4, page 193)

Fixed air was further studied by Joesph Black.  He was the first to recognize that this gas was burned off during the exhalation phase of respiration.   He discovered it "was deadly to animals, and could distinguish a flame." (3) (4, page 193-194)

Joseph Black (1728-1799)
Oxygen was first described in 1740 by Alexander Ferguson, yet it wasn't discovered until 1773 by Carl Wilhelm Scheele (1742-1786).  Scheele would later describe the discovery of a gas (empyreal air) that made candles burn brighter. The problem for him was that by the time he wrote about it someone else had already gotten credit. (2, page 282)

Unaware of the works of Scheele, and unaware that a third man -- Antoine Lavoisier (1743-1794) -- was doing similar research, (1) Joseph Priestly (1733-1804) published a work in 1772 called "Observations on different kinds of Air."

He described experiments he performed, and thus gained the interest of the science community. He "noticed that blood placed in an atmosphere of hydrogen or nitrogen gave off what we now refer to as oxygen. It was in this book that he described his discovery of oxygen, and for this reason he is given credit for its discovery, despite the works of other men.    (5, page 517)

Joseph Priestly (1733-1804)
He also observed that mice living in an environment with supplemental oxygen lived longer than mice who breathed normal air.  This was the first proof of the therapeutic benefits of supplemental oxygen.  (2)

Priestly then concluded the work of Michael Servetus, who noticed that the lungs changed the color of the blood and were the reason arterial blood was a brighter color.  Priestly proved that oxygen is inhaled into the lungs and exchanged from the alveoli to the capillaries and then into the arteries.

I think it's interesting to note why Priestly referred to oxygen as "dephlogisticated air."  It's explained best here:  
(Priestly's) experiments were sound, but his views on respiration were erroneous, vitiated as they were by his belief in the old theory of "phlogiston" introduced by (George) Stahl (1659-1734) in 1697. Phlogiston was the material and principle of fire, not fire itself, and respiration, according to Priestley, was a phlogistic process, whereby the phlogiston absorbed by animals with their food was discharged. Venous blood was phlogisticated, arterial blood dephlogisticated; a clot of blood placed in "fixed" or phlogisticated air became very dark, but regained its red colour when it was transferred to oxygen or dephlogisticated air. This old theory was overthrown a few years later by Lavoisier, who extended and explained correctly the discoveries of Mayow, Black, and Priestley; he showed that there were differences in the so called phlogistic processes. (5, page 476)
Antioine Lavoisier (1743-1794)
Yet while Priestly is given credit for the discoverey of oxygen, it was Lavoisier who was given credit for the name. While each early discoverer gave the new element his own name (Priestly called it "dephlogisticated air), the term "oxygene" was chosen by Lavoisier because he believed his new molecule was the great 'acidifying principle in nature. Oxygen is Greek for generator of acids.(1)
Lavoisier believed oxygen was acidic in nature because of some of the things it did. For instance, Lavoisier discovered that oxygen was involved in the rusting of metals, the formation of dew, as well as the respiration of animals and humans. Because it created such changes he believed it was an acid.

Stephen Hales (1677-1761)
Lavoisier, working with Pierre-Simon Laplace, determined, in 1780, that the body's heat was a byproduct of combustion that takes place in the body.  So in this way he disproved Galen's theory that a body's heat was produced in the heart. He later determined this combustion took place both in the lungs and other places in the body. It was later proved by others that it was in the tissues that respiration occurs.  So this was the beginning of knowledge of respiratory exchange.  (5, page 476)

The rush to learn more about air was on. Hales continued his research, and he created a device he called a pneumatic trough that he used to collect both carbon dioxide and oxygen, and now he was certain that plants obtained their nourishment from this air. (4, page 193)

Henry Cavendish (1731-1810)
Henry Cavendish (1731-1810) discovered hydrogen, or what he referred to as "inflammable air." He "exploded a mixture of hydrogen and oxygen and thus proved that water was not an element, but a compound of two gases." (4, page 194)

It has since been discovered that oxygen is present in most acids.  So for this reason the name "oxygen" really isn't an appropriate name for oxygen.  Yet the name stuck.  (1)

Experiments on animals by these men, and many other men to follow, proved that oxygen was the essential element of life.

The first reported experiments using oxygen on humans was done in 1783 by Francois Chausier (1746-1848). His experiments involved patients who had consumption (tuberculosis) and were dyspneic. He also used it for asphyxiated newborns. His and other early experiments using oxygen proved oxygen could be therapeutic for respiratory disorders, such as any disorder that caused dyspnea.  (2)

Francois Chaussier (1746-1848)
Realizing there might be therapeutic benefits from oxygen, and perhaps a profit to be made, Thomas Beddoes (1730-1810)  opened up the "Pneumatic Institute" in Bristol shortly after its discovery.  This was the first of what would later be referred to as oxygen parlors, which became common in the 19th century.  (2, page 281)

Beddoes devised a system where any amount of oxygen could be added into the atmosphere of small compartments.  A patient would spend a certain amount of time in these compartments breathing supplemental oxygen.  He described the following as being treated satisfactorily with such oxygen therapy: obstinate ulcers, leprosy, spasms, cancer, dropsy, hydrocephalis, headache, poisoning by opium, paralysis, scofulous tumors, scorbutus, venereal, deafness, white swelling, melancholy, general dibility, continued fever, intermittent fever, and coldness of the extremities.  (2, page 281)

Thomas Beddoes (1730-1810)
Yet despite the therapeutic experiments of Beddoes, oxygen was not accepted by the medical community, perhaps mainly due to the fact there were not efficient and inexpensive devices for making it and delivering it to the patient.  (2, page 281)

Of course there was also no experiment that proved without a doubt the benefits of using it either.  (2, page 281)

After Beddoes oxygen wasn't used therapeutically again until a cholera outbreak in 1832. (2, page 281)

Still, investigators continued to learn more about the microscopic structures in the body responsible for the transfer of oxygen through the body.

In 1840 Hunefeld found crystals in the blood of earthworms, and essentially became the first to observe hemoglobin.  He is therefore the person credited with its discovery.

Hemoglobin is the essential protein on red blood cells that carries oxygen or carbon dioxide in the blood.

In 1862 Hoppe-Seyler described the transport of oxygen on hemoglobin, and in 1864 George Stokes (1819-1903) described why oxygen changes the color of hemoglobin, and therefore darkens arterial blood. (5, page 525)

In 1870, Pfluger described tissue oxygenation.

In 1857 Claude Bernard (1813-1878) described that the color of blood was changed from bright red to dark because the dark blood contained more carbon dioxide. (6, page 239)

Carl Ludwig (1816-1895)and others proved the change in color had more to do with oxygen's attachment to hemoglobin.  When oxygen is attached to the hemoglobin the blood is redder, and when oxygen jumps and carbon dioxide replaces it the blood becomes darker. (1816-1895)

This explanation better explains the difference in color between arterial (freshly oxygenated blood from the lungs to tissues) and venous blood (deoxygenated blood from tissues going back to the lungs).(6, page 239)

It wasn't until the mid 19th century, however,  that oxygen parlors became readily available for use.  They essentially create dan oxygen enriched environment for those who wished to inhale it try it, either therapeutically or for entertainment.  (2)

By the turn of the 20th century physicians knew why breathing was essential to life, and the process of inhaling oxygen and exhaling carbon dioxide was referred to as ventilation.

The first two decades of the 20th century would see an increased effort to determine the benefits of oxygen therapy, and to invent better technology of delivering it to patients.  These efforts would gain urgency due to poisonous gases used in WWI.

References:
  1. Gray, Alonzo, "Elements of Chemistry:  Containing the Principles of the Science, both experimental and theoretical," 1840, Massachusetts, page 118
  2. Brainbridge, William Seaman, "Oxygen in Medicine and Surgery -- a contribution with report of cases," New York State Journal of Medicine, 1908Vol. 8, June, No. 6, pages 281-295
  3. "Carbon Dioxide,"  Scienceclariied.com, http://www.scienceclarified.com/Ca-Ch/Carbon-Dioxide.html#b, observed the site on May 4, 2012 (this information is available at a variety of sources, although I chose to give sciencedaily.com credit)
  4. Magner, Lois N., "History of Life Sciences," 2002, 3rd edition, New York, Marcel Dekker
  5. Hill, Leonard, Benjamin Moore, Arthur Phillip Beddard, John James Rickard, etc., editors, "Recent Advances in Physiology and bio-chemistry," 1908, London, Edward Arnold
  6. Fruto, Joseph S, "Proteins, Enzymes, Genes: The Interplay of Chemistry and Biology," 1999, New York, Yale University

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