There are two fingers,a right and a left.Thay can spring out a bit to pass around the shell.
They multi task. When down low,as the cartridge stops release a shell from the mag tube,these fingers catch it.As the slide begins to move forward,they function as lifters.
As the forward motion of the slide continues,these fingers spread enough to pass around the diameter of the shell. Then they rest high in the receiver till the round is fired.
Then as the side is pulled to he rear,once the hull clears the chamber.these fingers sweep down,flinging the hull out the bottom of the receiver.
One modern problem that CAN show up with the I-37 has to do with modern ammo. he older shells had the case heads formed of brass,which was ductile enough to form a good,distinct rim with maybe a slightly larger diameter and a fairly sharp inside corner radius.
Today's plated steel case heads don't form as easily.The rims have a larger inside corner radius and the OD may be smaller. The Ithaca's dual hook extractors just don't have enough rim to grab.(In SOME cases!! Your I-37 may work fine!!)
When you have a failure to extract, the hull occupies the chamber. The shooter pulls the slide back,and another round feeds into the lifters.
Now that round cannot feed into the chamber, but the lifters prevent he new round from exiting the bottom. There is no side ejection port to shake it out of. And access to the hull in the chamber is a problem. Its a tie -up!!
In my experience,the immediate action is pretty easy and quick.
The bolt is already open,so the extractors are free of the extractor slots in the barrel. The barrel is easily removed by twisting the mag tube cap clockwise. That releases the underlug of the barrel from the mag tube . Twist the barrel 1/4 turn counter clockwise. The barrel has interrupted threads,so you will then be able to slide the barrel out of the receiver. The live round will shake out and the hull will flick out easily.
I love the I-37, its a favorite! But that weakness may be a consideration for an I-37 combat shotgun