Cancer takes the breasts, the chest and the rib cage, and in many versions the stomach. The sign being cardinal, watery and ruled by the Moon, the region was read for complaints of fluid, of digestion and of the emotions, which the older physiology did not separate from the body as sharply as modern medicine does. The association with the breasts and with nourishment ties the sign to the Moon's significations of the mother and of feeding, and medical astrology of the medieval and early modern period used the sign in questions of nursing and of infant health. The atlas records this as history. Modern medicine has no place for it, and the historical confidence with which such judgments were made in matters of women's and infants' health is one of the less happy parts of the record.
Manilius sets the doctrine out twice in the Astronomica, once in the second book and again, in a related but not identical passage, in the fourth, which is itself evidence that melothesia was treated by the poem's Roman audience as an established piece of astrological doctrine worth restating rather than a single aside; modern Manilius scholarship generally reads the fourth-book passage as the fuller and more carefully worked-out of the two. Cancer's place in the sequence, following Gemini's arms and preceding Leo's heart, situates the chest and breasts at roughly the body's midpoint in the head-to-foot ordering, matched to the sign that, as the first cardinal water sign, opens the second quarter of the zodiacal year.