Meru, the Axis of the Lung-Globe

 The two primary bronchi serve as the front and back of Meru. The portion being spoken of in reference to the movement of the sun (to and from Meru) would be viewed as the front of the mountain and automatically, the other bronchus will be its back. 

Meru which is code for the two primary bronchi, is imagined by the ancient poet-anatomists as situated at the centre of the (respiratory) world. It divides the world into two parts, the world lying to the north of Meru and the world lying to its south. 

The sun, in either part, cannot cross the summit of Meru which is a kind of an axis for the microcosm. Its movement is only towards the primary bronchus and back (towards the distalmost end of the lung, relative to the hilum). But of course, when the earth rotates, as it were, with reference to the primary bronchus, the "front" and "back" also are interchanged. The movement of the sun now become defined with respect to the other bronchus. 

Speaking with reference to the bronchus that is "front," as the sun cannot cross this portion of Meru, the other ("back") portion always remains enveloped by darkness. 

Mid-day is defined at the top of Meru. As the sun approaches Meru, its brightness goes on increasing and as it takes the reverse route, towards the alveoli, its brightness goes on diminishing. It is midnight at the level of the alveoli. 

When the sun starts from one side of Meru it is noon there and midnight in the opposite location on the globe ie at the other primary bronchus. Then, as it travels in its chariot through the various spots of the lung, it is as if he gradually moves away from the corresponding locations. His intensity diminishes and he sets and eventually night falls and there is midnight at the level of the alveoli. In the other part of the lung-globe, the denizens of the locations opposite to those where noon, evening, night and midnight occur, experience respectively midnight, dawn, morning and noon! 

Change in the Direction of Movement 

Again, as the sun starts from the region of the alveoli, it is midnight there (and noon in the opposite side of the globe). His intensity increases as he moves towards the primary bronchus (Meru) and he now rises and the denizens of the locations falling on his path witness dawn, morning and noon. The denizens in the opposite part of the lung-globe would now experience evening, night and midnight!

The Animals in the Puranas

 It is the different components and sub-structures of the bronchial tree that masquerade as the different animals like the cow, the bullock, the tortoise, the horse, etc.

In the Mahabharata (Book 6: Bhishma Parva: Jamvu-khanda Nirmana Parva: Section IV), we have Sanjaya narrating to Dhrtarastra the fourteen species of animals:

These fourteen, O king, complete the tale of domestic and wild animals, mentioned, O lord of earth, in the Vedas, and on which the sacrifices rest.

The mobile and the immobile creatures (7 wild animals + 7 non-wild ones + 5 kinds of vegetation = 19) taken together with the five great elements make up the group of twenty four, collectively referred to as the “gayatri:”

Twenty-four in all, these are described as Gayatri (Brahma) as is well-known to all. He who knows these truly to be the sacred Gayatri possessed of every virtue, is not liable, O best of the Bharatas, to destruction in this world.

On the Manasottara Mountain

 The Manasottara mountain is a key entity appearing in the astronomical depictions of the Puranas. The sun is said to revolve round Manasottara. Because of this fact pointing to its central location, we hold it to be the heart.

Manasottara is said to go like a ring across all the five continents starting with Plaksa. The heart has a ring-like outline and it goes across the regions of the lung.

The Chariot of Mercury

 The chariot of the son of the Moon Mercury is composed of the fiery and windy material. [Therefore Mercury is associated with the p. artery. It is clear.]

Mercury moves on drawn by its eight horses [branches of p. artery]. [The chariots of the different planets are to be understood in the light of the hierarchical model. Thus the chariot of each succeeding planet would be a substructure of the chariot of the preceding (upper level) planet.]

On the Meaning of "Afternoon"

 In the Visnu Purana we have the pitrs partaking of the nectar of the moon in the "afternoon," when the moon consisting of just two digits, is said to be reduced to a fifteenth part of its original form. This can only be at the level of either the primary or the secondary bronchi. So it must be these generations of the bronchial tree that are designated as the "afternoon." This also makes perfect sense in the light of the statement that it is always mid-day over Mt Meru. 

The Hierarchy of the Chariot

 The primary and secondary parts of the bronchial tree (or the pulmonary arterial and venous trees) may be compared to the carriage of a chariot and the various parts of a chariot like the yoke and the axle. These parts connect the carriage with the parts that do the job of "moving" and "transporting," viz. the wheels and the horses.

The "horses," which are the conduits really coming after the "wheels," do the actual job of extending the higher-level bronchi, the carriage, as it were, into the deepest and the farthest realms of the lung. The hierarchy inherent in this metaphor of the chariot, therefore, is as given below:

1. the carriage
2. the yoke and the axle
3. the wheels
4. the horses

This is the general conception. However, in the case of the chariot of the sun, the wheel and the horses seem to occupy the same position.

The Orb of the Moon

 By the orb of the moon, the pulmonary venous conduit is meant. So when it is said that the Ganga overfloods the orb of the moon emerging from the foot of Visnu, it means the flow of oxygenated blood through the pulmonary venous conduit. The origin of the Ganga, standing for the origin of the entire circulatory flow, is (rightly) taken to be the flow of oxygen emanating from the alveoli (the "feet dust" of Visnu) mixing with the "water" in the capillary networks.