Jerusalem, Plate 12, (E 156)
"And the Four Points are thus beheld in Great Eternity
West, the Circumference: South, the Zenith: North,
The Nadir: East, the Center, unapproachable for ever.
These are the four Faces towards the Four Worlds of Humanity
In every Man. Ezekiel saw them by Chebars flood.
And the Eyes are the South, and the Nostrils are the East.
And the Tongue is the West, and the Ear is the North.
And the North Gate of Golgonooza toward Generation;
Has four sculpturd Bulls terrible before the Gate of iron.
And iron, the Bulls: and that which looks toward Ulro,
Clay bak'd & enamel'd, eternal glowing as four furnaces:
Turning upon the Wheels of Albions sons with enormous power.
And that toward Beulah four, gold, silver, brass, & iron:
And that toward Eden, four, form'd of gold, silver, brass, &
The South, a golden Gate, has four Lions terrible, living!
That toward Generation, four, of iron carv'd wondrous:
That toward Ulro, four, clay bak'd, laborious workmanship
That toward Eden, four; immortal gold, silver, brass & iron.
The Western Gate fourfold, is closd: having four Cherubim
Its guards, living, the work of elemental hands, laborious task!
Like Men, hermaphroditic, each winged with eight wings
That towards Generation, iron; that toward Beulah, stone;
That toward Ulro, clay: that toward Eden, metals.
But all clos'd up till the last day, when the graves shall yield
The Eastern Gate, fourfold: terrible & deadly its ornaments:
Taking their forms from the Wheels of Albions sons; as cogs
Are formd in a wheel, to fit the cogs of the adverse wheel.
That toward Eden, eternal ice, frozen in seven folds
Of forms of death: and that toward Beulah, stone:
The seven diseases of the earth are carved terrible.
And that toward Ulro, forms of war: seven enormities:
And that toward Generation, seven generative forms."
Milton, Plate 5, (E 98)
"And this is the manner of the Daughters of Albion in their beauty
Every one is threefold in Head & Heart & Reins, & every one
Has three Gates into the Three Heavens of Beulah which shine
Translucent in their Foreheads & their Bosoms & their Loins
Surrounded with fires unapproachable: but whom they please
They take up into their Heavens in intoxicating delight"
In the world of generation man is not Fourfold as he is in Eternity, but is Threefold. In the south is his head, in the east is his heart and in the north is his loins. The west is vacant, or the Western Gate is closed. The body, the fourth aspect in Eternity, no longer gives access to the real world of Eternity. Tharmas, the Zoa of the body, no longer has the ability to provide the integrating force which facilitates the unity of man.
Milton O. Percival gives us his wisdom on this subject in William Blake's Circle of Destiny, (Page 295):
"Note 15.36. cosmic man: That south, east, and north are the head, heart, and loins will not, I suppose, be questioned. The evidence is explicit. The evidence for the west being the Body may be briefly summarized. The west is 'outwards every way.' As the fall begins, Tharmas and Enion (the dual regents of the west) are said to constitute Nature (the cosmic body). At this point also Enion weaves a 'filmy woof' containing Tharmas; this is his new conception of the physical universe. As the fall progresses, it is the world of Tharmas which troubles Urizen (the Mind). At the time of the Flood Tharmas appears as the 'rough demon of the waters,' an overwhelming multiple and material universe. It is he who commands the universe to be rebuilt in the forms of 'death and decay'. The fall drags Enion into the indefinite of matter - into the Grave, whence she speaks with a comprehensive knowledge of the suffering of nature. As regeneration begins and the unity of Eden begins to be restored, Albion is said to gather 'the scattered portions of his immortal body.' The unity of Eden, which is placed in Tharmas's western region, is suggested by the fact that the Eternals live there in 'perfect harmony,' meeting together as 'One Man.'"
The Threefold sexual man of generation cannot be returned to the Fourfold complete man of Eternity unless heart, head, loins and body regain the ability to function in 'perfect harmony' through the opening of his Western Gate.
Four Zoas, Night VII, PAGE 95  (SECOND PORTION), (E 368)
"If we unite in one[,] another better world will be
Opend within your heart & loins & wondrous brain
Threefold as it was in Eternity & this the fourth Universe
Will be Renewd by the three & consummated in Mental fires
But if thou dost refuse Another body will be prepared"
Genesis 3 Therefore the LORD God sent him forth from the garden of Eden, to till the ground from whence he was taken.
 So he drove out the man; and he placed at the east of the garden of Eden Cherubims, and a flaming sword which turned every way, to keep the way of the tree of life.
Blake's Illustrations to Milton's Paradise LostThe Expulsion of Adam and Eve from the Garden of EdenButts Set 1808