Finally, some account must be given of pneuma. This concept—literally “breath”, but endowed with various kinds of technical significance and explanatory power in the previous philosophical and medical traditions—stands in an important, though somewhat problematic, relation to the theories of both elements and the soul. Its precise connection with the former is not made entirely clear, and pneuma is not standardly mentioned in Galen’s various accounts of the constituents of the body and the changes which it undergoes in health and disease. However, it plays an important role in his physiology, especially in PHP and UP. Here, two forms of pneuma, the “vital” (zõtikon) and the “psychic” (psuchikon) correspond to two major organs and systems in the body. Vital pneuma communicates vital (involuntary) function and tension through the arteries, psychic pneuma communicates perception and voluntary motion from and to the brain, through the nerves. It is possible here again to posit a Stoic influence in the central role accorded to pneuma in the account of vital, and especially psychological, function. Galen even floats the notion of the identity of soul and pneuma; that, however, is not his considered view of the matter, which is rather that the pneuma functions as the soul’s “first instrument” (see §7.2 below). Moreover, Galen’s theory in this area is fundamentally anatomical in nature, and certainly does not adopt Stoic metaphysical views in this area; its connections with the anatomically based medical theories of Herophilus and Erasistratus seem much more relevant than that more abstract and metaphysically based understanding of pneuma and its function (see Singer 2020b; further von Staden 2000; Rocca 2020; van der Eijk 2020).