Besides the primary elements, there are a number of secondary types of matter, material forms derived from the primaries. They are :

(a)  Five sensory receptors.
These are the sensitive tissues of the sense faculties, eye, ear, nose, tongue and body. The sensitive matter by reason of which eye can receive sight, nose can receive smell, ear can receive sound, tongue can receive taste and body can receive touch sensation.

(b)  The first four sense data.
Colour, sound, smells and taste are also secondary types of matter. The touch sensation however, is provided by the primary elements themselves.

(c)  Life faculty
The faculty which vitalizes the body and keeps it alive.

(d)  Mental base
Organs and nerve tissues which function as support for consciousness in the thought process.

The aggregate of form comprises the entire material side of existence. The mental side is distributed amongst the other 4 aggregates.