The Fly (1958) http://uk.imdb.com/Title?0051622
Directed by Kurt Neumann.
A scientist studying matter-transmission does not notice a fly in the compartment when he transmits himself.
With David Hedison, Patricia Owens, Herbert Marshall, Vincent Price.
I really loved this film as a kid.
Sequels were: Return of the Fly (1959)
Curse of the Fly (1965)
I don't know if it was the original film or a sequel, but there is a scene with cells containing all the results of failed experiments.
The special effects are rubbish.
The fly with a little man's head on it, is cheesy, but this was made in 1958.
Vincent Price at his best.
The remake by David Cronenberg is more grisly, has much better special effects, but doesn't really do more than update it.