Chemical Penetration, Causality, Intussusception

In the Metaphysical Foundations of Natural Science, Kant distinguishes between 'mechanical' and 'chemical' penetration, observing that the former "does not act by its own force", thereby implying that the latter does.  However, since he proceeds to develop a theory of Causality for mechanical events only, he leaves undetermined the status of chemical penetration in that regard.  Perhaps he anticipates that Newton's Third Law of Motion, which he grounds in the concept of reciprocal causality, cannot account for chemical penetration.  For, perhaps he recognizes that reciprocal causality entails distance between its factors, whereas chemical penetration consists in 'intussusception", as he terms it, i. e. in no distance between its factors.  So, in segregating Chemistry from what is generally known as 'Physics', he leaves it without a concept of Causality.