On the Identity of Garuda, the Solar Bird

 As we have seen previously, the entire bronchial tree was divided into three portions by the ancient anatomists. As in modern anatomical literature, these three divisions naturally suggested themselves by virtue of their clear functional and histological distinctions. The conducting division of the lung may be divided into a bronchial division and a bronchiolar division. The bronchioles, as indicated previously, were viewed as "birds" by the poet-anatomists. The absence of the outer layer of cartilage which is a marked feature of the bronchial conduits, imparts mobility and elasticity to the bronchioles. 

The region of the bronchioles which extends to the level of the acinus – the (actual) respiratory zone arrived at after 15 levels of branching of the bronchial tree – was again given the special name of "Bhuvar Loka" by the Puranics; the region where the "birds" fly.

Considering all these facts, it becomes clear that Garuda, the chief of birds, is the primary bronchiolar conduit. It collects the amrta (flow of oxygen molecules) from the sun and is  "suvarnamaya," golden; being adorned by the flow of oxygenated blood emanating from the bronchial artery. Garuda is also sometimes referred to as a "solar bird" and it is easy to understand why – it is part of the system of "rays" of the sun (the bronchial innervator).