A plaque remaining from the Big Apple Night Club at West 135th Street and Seventh Avenue in Harlem.

Above, a 1934 plaque from the Big Apple Night Club at West 135th Street and Seventh Avenue in Harlem. Discarded as trash in 2006. Now a Popeyes fast food restaurant on Google Maps.

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Entry from September 12, 2010
“When you hear hoofbeats, think of horses, not zebras”

“When you hear hoofbeats, think of horses, not zebras” has been a popular medical proverb since about the 1950s. The saying means that one (such as a doctor) should look for the expected cause first, rather than the exotic.
Dr. Theodore Woodward, who taught at the University of Maryland School of Medicine in Baltimore, told his students, in the 1940s, “Don’t look for zebras on Greene Street” (a street outside the medical school). Some websites give undocumented credit for the saying to Harley S. Smyth.
“When you hear hoofbeats in the hall, don’t look for zebras” has been cited in 1964 as a “folk truth.” The saying, while used mostly in the medical field, is also applicable to business and government.
Zebra (medicine)
Zebra is a medical slang term for a surprising diagnosis. Although rare diseases are, in general, surprising when they are encountered, other diseases can be surprising in a particular person and time, and so “zebra” is the broader concept.
The term derives from the aphorism “When you hear hoofbeats behind you, don’t expect to see a zebra”, which was coined in a slightly modified form in the late 1940s by Dr. Theodore Woodward, a former professor at the University of Maryland School of Medicine in Baltimore. By 1960, the aphorism was widely known in medical circles.
As explained by Sotos, medical tyros are predisposed to make rare diagnoses because of two synergistic cognitive phenomena: (a) the availability heuristic (“events more easily remembered are judged more probable”) combined with (b) the well-known phenomenon, first enunciated in Rhetorica ad Herennium (circa 85 BC), that “the striking and the novel stay longer in the mind.” Thus, the aphorism has a valid role in teaching medical students to be better diagnosticians.
Three master diagnosticians have noted, however, that cautions against making surprising diagnoses (e.g. of a rare disease) are not valid in practitioners with greater knowledge and experience:
In making the diagnosis of the cause of illness in an individual case, calculations of probability have no meaning. The pertinent question is whether the disease is present or not. Whether it is rare or common does not change the odds in a single patient. ... If the diagnosis can be made on the basis of specific criteria, then these criteria are either fulfilled or not fulfilled.—A. McGehee Harvey, James Bordley II, Jeremiah Barondess
A related, but distinct, term for an obscure and rare diagnosis in medicine is fascinoma.
Zebra Cards
Who Coined the Aphorism?
Then, in 1995 I (John Sotos, MD—ed.) made a presentation to a continuing medical education course at Hopkins. A member of the audience recalled hearing it during his medical training in the 1950s. He suggested I speak with his former chief, Dr. Theodore Woodward of the University of Maryland in Baltimore.
Dr. Woodward is now Emeritus Professor of Medicine at the University of Maryland. An infectious disease specialist, he is affiliated with the Baltimore Veterans Administration Hospital.
Dr. Woodward was most gracious on the telephone. He admitted that he probably had something to do with coining the phrase. His original admonition to medical trainees in the late 1940s was “Don’t look for zebras on Greene Street.” (The University of Maryland Hospital is located on Greene Street in Baltimore.) How this developed into the precise wording of the aphorism is still unknown. Nevertheless, it seems proper to credit Dr. Woodward with inventing it.
25 November 1964, Seattle (WA) Daily Times, “Date-Line” by Ele and Walt Dulaney, pg. 17, col. 3:
Better heed the foilk truth, “When you hear hoofbeats in the hall, don’t look for zebras.”—ELE AND WALT    
Google Books
The Reader’s Digest
Volume 84
1964 (Google Books dates might be inaccurate—ed.)
Pg. 130:
...blue eyes, then grinned and said tolerantly, “Jack, if you hear hoof- beats around here, you can usually bet they’re made by horses, not zebras. Fortunately, when somebody gets sick, the trouble is usually something common, not one of those exotic diseases they dramatize in medical schools.”
Google Books
Guide to Clinical Laboratory Diagnosis
By John A. Koepke
New York, NY: Appleton-Century-Crofts
Pg. 79:
As one “philosopher” put it: “When you hear hoofbeats, think of horses, not zebras.”
31 May 1975, Winnipeg (Manitoba) Free Press, “If You Hear Hoofbeats, Don’t Look For Zebras” by Melvin Maddocks, pg. 38, col. 5:
When the authors stated the repairman’s law of probability—if the car won’t start, first check the gas tank, etc.—it came out like this: “When you hear hoofbeats, don’t look for zebras (unless you are on the Seregeti Plain).”
Google Books
Vulvar Disease
By Eduard G. Friedrich
Philadelphia, PA: W. B. Saunders Company
Pg. 95: 
Hoofbeats usually mean horses not zebras.
Google News Archive
14 June 1977, Modesto (CA) Bee, “People’s doctor” by Robert Mendelsohn, M.D., pg. C11, col. 4:
I understand that in some medical schools one of the first things medical students are taught is, “When you hear the sound of hoofbeats, think of horses before zebras.” Often the most obvious explanation for a child’s behavior is the simplest, physical pain. These parents should run, not walk, to a university medical center.
—Fresno Mother
OCLC WorldCat record
When you hear hoofbeats, think of a zebra : talks on sufism.
Author: Shems Friedlander
Publisher: New York u.a. : Harper & Row, 1987
OCLC WorldCat record
Think zebras when you hear hoofbeats
Author: James P Gould
Publisher: Denver, CO : Keller, Burns, & McGuirke, 1989
Edition/Format: Book : English
OCLC WorldCat record
Review 2 When you hear hoofbeats, don’t think of zebras first
Publisher: 1989 Oxford University Press
Edition/Format: Internet resource : English
Database: OAIster
OCLC WorldCat record
When you hear hoofbeats, sniff the air: You remember the adage from medical school: “Think horses, not zebras.” Based on his experience with two frustrating patients, this FP offers a corollary
Edition/Format: Article : English
Publication: MEDICAL ECONOMICS -ORADELL THEN MONTVALE NJ- 73, no. 19, (1996): 107-118
Database: British Library Serials
OCLC WorldCat record
“When You Hear Hoofbeats, Think Horses, Not Zebras”: A Folk Medical Diagnostic Proverb
Author: L Dundes; M B Streiff; A Dundes
Edition/Format: Article : English
Publication: PROVERBIUM -COLUMBUS THEN BURLINGTON- 16, (1999): 95-104
Database: British Library Serials
Google Books
The medical science of House, M.D.
By Andrew Holtz
New York, NY: Berkley Boulevard
Pg. 27:
Who coined the term? Dr. Sotos says he searched for twenty years, and finally concluded that the best claim belonged to the late Theodore E. Woodward, M.D., who taught at the University of Maryland School of Medicine in Baltimore for nearly fifty years. Dr. Woodward was also nominated for a Nobel Prize, and received an award from President Franklin D. Roosevelt, for his role in developing treatments for typhus and typhoid fever.
Dr. Sotos says that beginning in the 1940s, Dr. Woodward admonished his medical students, “Don’t look for zebras on Greene Street,” referring to the street outside the University of Maryland medical school. Over time, the advice became more general: “When you hear hoofbeats behind you, don’t expect to see a zebra.”
All About Horses: Pair Of Toast
hoofbeats horses not zebras
Posted December 29, 2008 By admin
Can you state the origin of this folklore “If you hear hoofbeats, think horses not zebras.”?(go to details)?
I do think this is one of those many sayings that people use without giving credit to the source, but for someone else to take credit for it is a big no-no. Maybe it should be called Aristotle’s Razor.
Hippocrates is known as the Father of Medicine. Was the concept originally his?
Two sites I explored list the source as unknown and another attributes it to Dr. Thomas E. Woodward. It does make one wonder what to believe.
It is a good concept. I always tell my clients let’s try the simple things first, and many times it works.
Another site credits the quote to Harley S. Smyth.
What the heck????????

Posted by Barry Popik
New York CityGovernment/Law/Military/Religion /Health • Sunday, September 12, 2010 • Permalink

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