Page 434 - Complete Works of Dr. KCV Volume 1

the cortex and the supra cortex, and the nervous system for the preservation of the body with the entire organism. The nervous system may be considered to be the fire-tattva, the glands, water tattva and the Sukshma Sarira is formed not out of the gross vayu which pervades the body and helps the organism to live but is formed out of akasa and the sukshma akasa which is indivisible and subtle. The link between the sthula and the sukshma sarira is supplied by vayu in its subtler phase. That the vayu extends twelve digits above the head is a suggestion in point. And it is suggested that through control the entire prana must be made to be neither more nor less than the physical body. That leads to complete control of the physical body and is perfect integration of all levels, perfect harmonization of the functions of the body. This is one definition of yoga according to the Sandilya Upanishad.
Regarding chakras we have no mention of them by the Sariraka and the Garbha Upanishads which are considered to be physiological Upanishads.
The Garbha mentions the Sushumna and the coursing of vayu in the body as prana, the original prana, which descends through the Sushumna to be the heart at the time of birth. Thus at the time of the Garbha and the Sariraka either the literature with regard to the chakras have not been known generally or else their descriptions being merely the physical gross descriptions, they have not referred to the nadis and chakras which belong to the Sukshma Sarira and could be seen only by Yogis.
Whilst it is true that the neurons are instruments of mind and act as the medium of the bodily expression, it is not absolutely true that the phenomena of mind "can only be correctly interpreted in terms of neurons and neuronic arcs" for the neurons are just one stage of evolution of the organism and not the most important, but along with other systems they form an inseparable function in the body.
The neural explanations as much as the glandular explanations do not make their explanations perfectly acceptable in psychic life in both cases with all good intentions after a search for behaviour and experimentation of reactions, the motive of an action or an expression is not found - that subtle mark which makes all the difference does not make any difference in behaviour of the internal organs nor external organs. This crux of the