The following is quoted from Griffith's electrodynamics book, 3rd edition:

> 
> Suppose we have some charge and current configuration which, at time t, produces fields $\mathbf E$ and $\mathbf B$. In the next instant, $dt$, the charges move around a bit... According to the Lorentz force law, the work done on a charge $q$ is:
>  \begin{split}
> \mathbf F \cdot dl &=q(\mathbf E + \mathbf v \times \mathbf B) \cdot \mathbf v dt\\
> &=q\mathbf E \cdot \mathbf v dt\\
> &=\rho dv \mathbf{E} \cdot \mathbf{v}dt\\
> &=\mathbf{E} \cdot\mathbf{J} dvdt\\
> &=\left[ \frac{1}{\mu}\_0 \mathbf{E} \cdot (\nabla \times \mathbf{B})-\epsilon\_0 \mathbf{E} \cdot \frac{\partial \mathbf{E}}{\partial t} \right ] dvdt
> \end{split}
> 
> 
> 

The last equality comes from Ampere-Maxwell's law: the $\mathbf{J}$ in this equation must be the $\mathbf{J}$ of the source charges, which in turn gives rise to the source magnetic field $\mathbf{B}$, rather than the $\mathbf{J}$ of the external (test) charges under the influence of $\mathbf{B}$, since that is the meaning of the Ampere-Maxwell's law.

The above paragraph seems to suggest that the fields created by a particular charge and current distribution can actually exert forces on their sources. But as far as my understanding goes, a field only exerts forces on external charges (test charges). 

My question is:

1. Is there something that I am missing in interpreting the above paragraph?
2. Can electric and magnetic forces act on their sources?