Sunday, December 27, 2009

David Hendricks Bergey

David Hendricks Bergey was born on the Mennonite meetinghouse farm in Shippack township, Montgomery County, Pennsylvania on December 27, 1860. As was the custom for boys on the farm he attended school during the winter and worked the farm during the summer. After turning 18 he attended private and normal schools and taught two winters in rural schools before he decided to study medicine. He started his medical training in the office of Dr. Samuel Wolfe of Shippack, PA.

He went to the University of Pennsylvania and graduated with a B.A. and M.D. simultaneously in 1884 at a time when the discoveries of Luis Pasteur and Robert Koch was causing much discussion in American bacteriology circles. Dr. Bergey went to work in the laboratory of Dr. Henry Formad, who had made two visits to Dr. Koch's laboratory. It was here that Dr. Bergey was introduced to bacteriology.

For nearly ten years Dr. Bergey practiced medicine in North Whales, PA, before returning to the University of Pennsylvania in 1893 first as a student and then as a Scott Fellow in Hygiene in the newly built laboratory of Hygiene. In 1895 he was appointed assistant in chemistry, in 1903 he made assistant professor and in 1926 full professor of hygiene and bacteriology.

Dr. Bergey was responsible for numerous publications during his lifetime but he is best remembered for the manual of bacterial classification that is named after him. The first edition of the manual was published in 1923 by the Society of American Bacteriologists (now the American Society of Microbiologists). Dr. Bergey served as the chairman of the editorial board for the manual. Dr. Bergey had begun preparing the manual soon after he had been the president of the society in 1915 in order to replace the old system of bacterial classification outlines to fit newer knowledge. The manual, which still bears his name, has been constantly revised and is still used today as a standard reference of bacterial classification.

Dr. Bergey died on September 5, 1937. The Bergey award and Bergey medal, awarded for contributions to bacterial taxonomy, given out annually by the Bergey manual trust, are named after him.


Breed, Robert; "David Hendricks Bergey"; Journal of bacteriology(1938)vol.35:p.I2-345

"History of Bergey's Manual" at

David Hendricks Bergey, Wikipedia entry

Bergey's Manual Trust Website

Sunday, December 20, 2009

Thomas Graham

Thomas Graham was born in Glasgow on December 21, 1805 the the eldest of seven children of a merchant father. After attending preparatory school and high school he started classes at the university of Glasgow in 1819, where he studied under Thomas Thompson. He remained there for seven years taking an M.A. in 1826. His father wanted him to go into the Scottish church, but Thomas showed an aptitude for mathematics and science and against his father's wishes he commenced on a career in science.

Graham was a lecturer in chemistry at the Mechanics Institution in Glasgow and then he was appointed professor of chemistry at Andersonian University in Glasgow. It was at this point that he was able to devote more time to experimentation and the seven years he spent at Andersonian were busy. In 1837 he was appointed professor of Chemistry at London University (now University College, London) where he occupied the chair until 1855 when he succeeded Sir John Herschel as Master of the Mint and remained in that positon until he died.

Graham is best remembered for his discovery that under the same temperature and pressure the rate of effusion of a gas is inversely proportional to the square root of its atomic mass. A demonstration of this can be found here. Basically this law means that the smaller the atomic mass of the gas the faster it will diffuse. Graham was awarded the Keith prize in 1834 by the Royal Society of Edinburgh for this discovery.

Graham is also remembered for his invention of dialysis. Between 1861 and 1864 Graham, while he was studying the ability of dissolved substances to pass through a membrane, noticed that substances that crystallized well like salt passed well through the membrane and substances that did not crystallize like gelatin did not. He distinguished these two classes of substances as crystalloids and colloids. This discovery led to the dialysis that is done on kidney patients today.

Graham is also remembered for is characterization of phosphates in solution. For all of these discoveries Graham was awarded the Copley medal of the Royal Society in 1862.

Graham died on September 16th, 1869.


Williamson, A.W.; Obituary in Nature, Volume 1, (1869) p. 20-22

Obituary in the Proceedings of the Royal Society; Volume 18 (1870) p. xvii-xxvi

Obituary in the Lancet; Volume 2 (1869) p. 456-457

Plimer, Robert Henry Aders; Practical Organic and Biochemistry Chemistry; Logmans, Green and Company; 1920

Sunday, December 13, 2009

Mary L. Caldwell

Born on December 18, 1890, Mary Letitia Caldwell was the daughter of Presbyterian missionaries working in Colombia. She attended high school in the United States and then attended the Western College for Women in Oxford, Ohio, graduating in 1913. She taught there for five years following her graduation. She then went to Columbia University, where she studied under Henry S. Sherman and obtaining a M.A. and a Ph.D. in organic chemistry. She stayed at Columbia first as an instructor and then a full professor in 1948. She was the only woman to be a senior chemistry faculty member at the time.

Mary Caldwell's research centered on enzymes that use starch as a substrate, particularly amylases. She was the first person to purify porcine pancreatic amylase, an enzyme that is used both in industry and research. She also established that amylase is a protein. Amylase is an enzyme that breaks down starches into individual carbohydrate units.

Although Mary Caldwell suffered from a progressive muscular disorder, she never changed her office on the 9th floor of Chandler Hall. She retired in 1959 and was awarded the Garvan Medal by the American Chemical Society in 1960.


Mary Letitia Caldwell, Journal of Chemical Education online

Ogilvie, M.; The Biographical Dictionary of Women in Science: Pioneering Lives From Ancient Times to the Mid-20th Century; p.220-1; Routledge; 2000

Barbosa, Patty; "Mary Letitia Caldwell"; in The Data Bank of Scientists at

Sunday, December 6, 2009

Theodor Schwann

Theodor Schwann was born on December 7, 1810 in Neuss, near Dusseldorf, in Rhenish Prussia, which at the time was a providence of the French Empire. Theodor was the fourth of thirteen children of a goldsmith who had set up a successful printing business. From his father Theodor inherited a proclivity for working with his hands which suited him well in his scientific career. He spent the play hours of his childhood building miniature physical instruments from primitive materials.

Theodor attended a Jesuit college in Cologne and went to the University of Bonn, where after initially studying theology, his natural inclination for science led him to study medicine, studying under Johannes Muller. Muller, recognizing Schwann's abilities, made him an associate and they researched the motor and sensory roots of spinal neurons and blood coagulation. Schwann migrated to Warzburg, and then to Berlin to finish his doctorate and again work with Muller.

In Berlin Schwann became an aid at the Anatomical Museum of which Muller was the director. It was during this time that Schwann laid the basis for the study of nervous and muscle tissue that others would elaborate on. Schwann was one of the first to deal with living tissue on only a chemical and physical basis, ignoring the aid of "vital force". Schwann also discovered that alcoholic fermentation and the fermentation that causes putrefaction were carried out by microbes, a discovery that was ignored and even ridiculed at the time. Adept with the microscope, Schwann was the first to find the thin layer of cells on the inside of blood vessels, which would later be called the endothelium and confirmed the observation of Robert Remark of the cellular sheath around nerve cells, the cells of which would later be named after Schwann.

All of this work would have been enough for Schwann to be considered a great scientist, but Schwann is most famous for his elaboration of the cell theory of biology. In 1839 Schwann published "Microscopical Researches into the Accordance in the Growth and Structure of Animals and Plants", in which he continued the work that Matthias Schleiden had started with plants and identified the cell as the basic unit of living tissue in animals. The discovery was prompted when Schwann was having lunch with Schleiden. Schleiden was describing the nuclei he had found in plant cells and Schwann recognized that he had seen similar structures during his microscopic examinations of animal tissues. The two went to the anatomy theater (this was at Louvin where in 1839 Schwann had been appointed professor of anatomy) where Schwann showed Schleiden animal cell nuclei. From this point on Schwann dedicated his research to studying animal cells.

After all of his early success Schwann did little active research. In 1848 he was called to the University of Liege, where he remained till his death. In 1875 he published an indignant pamphlet denouncing the Catholic clergy for claiming that he testified in favor of the miraculous nature of the appearance of stigmata on Louise Lateau and he died in 1882 at the age of 72.


"Theodor Schwann"; Proceedings of the American Academy of Arts and Sciences; Vol. 17 (1882) p. 460-1

"Heroes of Medicine: Theodor Schwann"; The Practitioner; Vol. 59 (1897) p.498-501

Kettenmann, Helmut; Ransom, Bruce R.; Neuroglia; Oxford University Press, USA; 2004

Leon, Fredericq; "Sketch of Theodor Schwann"; The Popular Science Monthly; Vol. 37 (1897) p.257-264

Otis, Laura; Muller's Lab; Oxford University Press, USA; 2007