Abstract methods vs Virtual methods

What IL code is emmited when you have an abstract method, and a virtual method? For C# below

public abstract class MyAbstract
{
    public abstract void Run(int x);
} 

public class MyConcrete
{
    public virtual void Run(int x)
    {
    }
}

The equivalent IL is:

// MyConcrete
.method public hidebysig newslot virtual instance void Run(int32 x) cil managed 
// SIG: 20 01 01 08 
{ 
    // Method begins at RVA 0x2133 
    // Code size 2 (0x2) 
    .maxstack 8 
    .language '{3F5162F8-07C6-11D3-9053-00C04FA302A1}', '{994B45C4-E6E9-11D2-903F-00C04FA302A1}', '{5A869D0B-6611-11D3-BD2A-0000F80849BD}' 
    // Source File 'C:\Examples\Example49\Program.cs' 
    //000040: { 
    IL_0000: /* 00 | */ nop 
    //000041: } 
    IL_0001: /* 2A | */ ret 
} // end of method MyConcrete::Run 


// MyAbstract
.method public hidebysig newslot abstract virtual instance void Run(int32 x) cil managed 
// SIG: 20 01 01 08 
{ 
    // Method begins at RVA 0x0 
} // end of method MyAbstract::Run

As you can see, MyConcrete.Run() actually contains op codes while MyAbstract.Run() as you'd expect, contains nothing. Abstract methods are virtual though which probably isn't a huge surprise either. Both of the above use the newslot keyword which indicates that it should override any existing space in the v-table for this method (as they are base classes there is nothing to override).