I'm trying to find the name and author of a short story I read years
ago (the story was written sometime between 1950 and 1975) about a
scientist who experiments on aligators, something to do with the
alligators had a heart defect or an inefficient reptilian heart.  So
he performs open heart surgery, and the alligators then begin to
become much bigger, much more inergetic, and begin to change into
dragons.  The scientist trys to keep them secure, but of course, they
escape and wreek havoc on the world.  Can you find this info?

Hello.

The story is "The Day of the Dragon" by Guy Endore. It was written in
1934.

There have been several Usenet discussions over the last few years
about this story:

On 9/8/96, in the newsgroup alt.horror, an individual named Nemo
mentioned
"'The Day of the Dragon' (about a scientist who reforms crocodiles'
hearts and makes them into dragons."
See the message in the archive of Google Groups:
http://groups.google.com/groups?selm=nemo-0809961500190001%40news.accessnv.com&output=gplain

On 9/3/2001, in the newsgroup rec.arts.sf.written, David Tate wrote:

"A scientist (physician?) is experimenting with crocodiles.  He notes
that the 2-chambered crocodile heart is very inefficient, leading to
poorly-oxygenated blood and sluggishness.  He (surgically? 
genetically?) alters some crocodiles to have efficient 4-chambered
hearts...
The 4-chamber-heart crocodiles sprout wings and start breathing fire,"

See the discussion that followed, also on Google Groups:
http://groups.google.com/groups?hl=en&lr=&ie=UTF-8&threadm=9d67e55e.0109041656.322f22a4%40posting.google.com&rnum=6&prev=/groups%3Fq%3Dendore%2B%2522day%2Bof%2Bthe%2Bdragon%2522%26hl%3Den%26lr%3D%26ie%3DUTF-8%26selm%3D9d67e55e.0109041656.322f22a4%2540posting.google.com%26rnum%3D6

SF Site, the Home Page for Science Fiction and Fantasy, provides this
list of anthologies that contain the story:
http://www.sfsite.com/isfdb-bin/pwork.cgi?2e6241

Here are used book listings for some of the various anthologies from
BookFinder.com:

"Zoo 2000" (1973) edited by Jane Yolen
http://www.bookfinder.com/search/?author=yolen&title=zoo+2000&submit=Begin+Search&new_used=*&currency=USD&mode=basic&st=sr&ac=qr

"Monster Mix" (1968) edited by Robert Arthur
http://www.bookfinder.com/search/?author=arthur&title=monster+mix&submit=Begin+Search&new_used=*&currency=USD&mode=basic&st=sr&ac=qr

"Alfred Hitchcock's Monster Museum" (1965)
http://www.bookfinder.com/search/?author=&title=alfred+hitchcock%27s+monster+museum&submit=Begin+Search&new_used=*&currency=USD&mode=basic&st=sr&ac=qr

search strategy: alligators, crocodiles, dragons, heart, story

I hope this helps. Good luck.

Excellent.  Thanks much juggler-ga.  I highly recommend the story (it
came to mind when I was watching the new "Reign of Fire" movie that
deals with a nasty plague of dragons creating a disutopic 2020).