  In this paper we calculate the Casimir energy for a massive fermionic field
confined between two points in one spatial dimension, with the MIT Bag Model
boundary condition. We compute the Casimir energy directly by summing over the
allowed modes. The method that we use is based on the Boyer's method, and there
will be no need to resort to any analytic continuation techniques. We
explicitly show the graph of the Casimir energy as a function of the distance
between the points and the mass of the fermionic field. We also present a
rigorous derivation of the MIT Bag Model boundary condition.
