TexasCHLforum.com

Without more details, I have to agree with gemini. Your pistol is specifically made for a .38 Long Colt Cartridge:
"The United States Army adopted the .38 Long Colt in 1892 and it remained in service until 1911, when the military adopted the .45 ACP and the M1911 autoloading pistol."

http://en.wikipedia.org/wiki/.38_Long_Colt" onclick="window.open(this.href);return false;

Depending on the age of your pistol, IMHO, I would not shoot modern .38 special ammo in your old gun, as it might not be able to withstand the higher chamber pressures of the modern rounds, and could result in a catastrophic failure....assuming that your gun is indeed chambered for a .38 Long Colt cartridge.

This might give you some more insight:

http://www.coltforum.com/forums/showthread.php?t=16742" onclick="window.open(this.href);return false;

I'd suggest taking it to a gunsmith and getting his opinion.