Yogi's are known to observe their own body with utmost attention and were able to find out things about the body which modern medicine and science also found out.
One such thing is nasal cycle.
The nasal cycle was studied and discussed in the ancient Indian yoga
of literature of pranayama. In the modern western literature, it
was first described by the German physician Richard Kayser in 1895.
A CT scan showing evidence of the nasal cycle. The more patent airway
is on the right of the image; the swollen turbinates congesting the
The nasal cycle is the unconscious alternating partial
congestion and decongestion of the nasal cavities in humans and other
animals. This results in greater airflow through one nostril with
periodic alternation between the nostrils. It is a physiological
congestion of the nasal conchae, also called the nasal turbinates
(curled bony projections within the nasal cavities), due to selective
activation of one half of the autonomic nervous system by the
hypothalamus. It should not be confused with pathological nasal
Also notice the similarity of this with Anulom Vilom Pranayama.