It may, however, be mentioned that it is really Prana which controls secretions
of glands and since Prana is amenable to thought, once knowledge of the working of
glands is acquired the Yogi can control all the physiological actions in the body, even
the movements of the heart and lungs. What a doctor tries to bring about by the action
of drugs the Yogi can bring about by the control and regulation of Pranic currents in
the body. The glands involved in these physiological actions have not been specified
by Patanjali, obviously, to prevent foolish people from dabbling in these matters and
injuring themselves.
- (By performing Samyama) on the Kurma-nadi steadiness.
Prana is of many kinds, each kind having special functions in the body and a
special Nadi as its vehicle. Kurma is one of the well-known varieties of Prana and the
particular nerve which serves as its vehicle is called Kurma-nadi. This variety of
Prana has obviously something to do with the motions of the body for by controlling it
the Yogi acquires the power to make his body motionless. This control can be ac-
quired, as usual, by performing Samyama on the Nadi which is its vehicle.
All the physiological devices working in the physical body are meant to carry
on their normal activities in an involuntary manner. But since each device is really the
vehicle of a principle or Tattva it is possible by gaining voluntary control over its
function to express that principle to any extent desired. It is this kind of voluntary con-
trol over the function of the Kurma-nadi which enables the Yogi to perform feats of
strength which appear miraculous to an ordinary person. But, of course, no real Yogi
will make a demonstration of this kind.