Picture - Cosmic Polymath

4o6 DESIGN IN NATURE
PLATE XCV
Plate XCV. illustrates the foetal and placental circulations ;
also the development of the blood-vessels and heart.
Fig. 1.—Circulation in the human fcetus (semi-diagrammatic). In this figure the darts show the direction in which the blood
flows. The quality of the blood is indicated by the colours of the blood-vessels. Thus the white blood-vessels contain arterial
blood, the black vessels venous blood, and the shaded vessels mixed blood, a, External surface of placenta ; b, internal surface of
placenta ; c, circulation in the head (mixed and venous blood) ; d, circulation in the arm (mixed and venous blood) ; e, circulation
in the leg (mixed and venous blood) ; /, venous circulation in the intestine ; w, venous circulation in stomach and spleen ; g, g, (j, umbilical
vein containing arterial blood from the placenta to the liver (») and ascending cava (o) ; h, h, h, umbilical arteries conveying
mixed blood from the hypogastric arteries (j) and body of foetus to placenta {a, h) ; i, continuation of umbilical vein (arterial blood)
k, ductus venosus (arterial blood) ; I, vena portas, containing venous blood from intestine (/), stomach {v), and spleen ; m, descending
aorta, dividing (;i;) into the common iliac arteries and containing mixed blood ; o, ascending cava, containing venous blood at lower
part and mixed blood at upper part ; s, ascending cava discharging its mixed blood through the right auricle and Eustachian valve
into the left auricle, from which it finds its way into the left ventricle (r) and thence into the ascending, transverse, and descending
portions of the aorta, from which it is distributed to the head and neck (c), the arms {d), legs (c), body and viscera (/, «') ; y, descending
cava discharging its venous blood into the right auricle and right ventricle (z). From the latter it finds its way into the right and
left lungs, which as yet are rudimentary and take no part in aerating the blood ; this function being vicariously performed by the
maternal portion of the placenta. The blood from the lungs {n) is discharged into the left auricle.
In this figure the blood-vessels (the placenta excepted) terminate in loops formed by the continuation of the arteries with the
veins. The capillary blood-vessels are omitted for the sake of simplicity. Drawn by C. Berjeau for the Author.
FiC4. 2.—Human umbilical cord composed of one vein {a), and two arteries (6), intertwining to form a symmetrical left-handed
spiral. Resembles spiral water-spout (Fig. 5), and the twining stems of the hop (Plate x.. Fig. 2, A). Two spirals at least are
necessary to produce symmetry, structures composed of one spiral being incomplete or lop-sided. Drawn from injected specimen
in the possession of the Author by C. Berjeau.
Fig. 3.—Diagram showing the course of the circulation in the human fcetus {vide arrows), rj', i, Umbilical vein, conveying
arterial blood from the placenta ; K, umbilical arteries, conveying venous blood to the placenta ; k, ductus venosus ; I, vena portfe
II, vena cava, inferior ; y, vena cava, superior ; s, Eustachian valve and right auricle ; q, right ventricle ; v, ductus arteriosus, uniting
aorta («) and pulmonary artery ; t, left auricle ; ) , left ventricle ; m, descending aorta ; x, common ihac artery, dividing into external
and internal iliac arteries ; j, hypogastric arteries, continuous with umbilical arteries (/i').
Diagram illustrating the relation existing between the maternal (»i) and foetal (re) portions of the placenta (human). The
maternal and fretal surfaces are represented as separated from each other by a certain interval (»!., re) to avoid confusion. They are
slightly uneven from the projection into them of the maternal and fcetal capillary vessels. During pregnancy the two surfaces
accommodate themselves so as to dovetail and fit accurately into each other. In the diagram the vessels represented by solid lines
contain arterial blood ; those represented by dotted lines venous blood, tii, Mucous lining of uterus, with nucleated cells on its
surface ; h, sub-epithelial, spheroidal, and fusiform corpuscles, embedded in connective tissue ; r, d, utricular glands lined with
epithelium, and opening on mucous surface of uterus. They pour utricular secretion into utricular space (m, n). This space is
mapped off, on the one hand, by the villi and coverings of the maternal portion of the placenta ; and on the other, by the villi and
coverings of the foetal portion of the placenta. The utricular secretion is necessary to a free osmosis between the maternal and
fcetal vessels, ra. Limiting membrane of fcetal portion of placenta covered with nucleated cells ; a, sub-epithelial, spheroidal, and
fusiform corpuscles embedded in connective tissue ; i, i, amnion; g, umbilical vein, conveying arterial blood to fcetus ; /;, umbilical
arteries, conveying venous blood from fcetus. The umbilical arteries and vein break up to form the villi of the fcetal portion of
the placenta ; these being directed towards similar villi (c, /), constituting the maternal portion. The maternal and foetal villi are
separated from each other by the utricular space {m, n) containing utricular secretion, by two layers of cells, by two membranes,
and by a certain proportion of connective tissue, spheroidal, fusiform, and other corpuscles (a, h). Goodsir regarded the placental
villus as consisting of a maternal and fcetal portion ; the maternal portion being composed of a membrane and nucleated cells, and
corresponding to in of diagram ; the foetal portion being composed of a membrane and nucleated cells, and corresponding to re of
diagram. Between the maternal and fcetal portions (as he termed them) of a placental villus, he represents a space which
corresponds to the space between m and n of diagram. This space he regarded as the cavity of a secreting follicle. Goodsir
has, it appears to me, appropriated the lining membrane of the maternal portion of the placenta (m of diagram) and added it to the
limiting or lining membrane of the foetal portion {n of diagram). Described and drawn by the Author from specimens in 1872.
Fig. 4.—Gravid human uterus about the end of the seventh month, a, ., Foetal portion of placenta ; h, umbilical cord ; c, body
of fcetus (after Dalton).
Fig. 5.—Shows the early and adult condition of the arterial system in the mammal.
A. Early state of the arterial system, showing the heart (a), with its two ascending trunks, giving oft' on each side five cervical
arteries which terminate in the vertebral arteries (A, V). The vertebral arteries unite below the heart to form the aorta (r).
B. Adult state of the arterial system, a, n, Carotid arteries ; h, h', vertebral arteries ; c, c, right and left subclavian arteries ;
d, d', right and left superior intercostal arteries ; c, left aortic arch which remains permanent ; f, right aortic arch which disappears
(after Dalton).
Fig. 6.—Shows spiral development of human heart.
A. Earliest form of foetal heart, a, Venous extremity ; b, arterial extremity.
B. Pretal heart twisted upon itself, a, Venous extremity ; b, arterial extremity.
C. Foetal heart divided into right and left cavities, a, Venous extremity ; /), arterial extremity ; c, c', pulmonary branches.
D. Fcetal heart still further developed, a. Aorta ; h, pulmonary artery ; c, c', pulmonary branches ; d, ductus arteriosus.
B. Heart of infant, showing disappearance of arterial duct after birth, a, Aorta ; b, pulmonary artery ; c, c', pulmonary
branches ;
d, ductus arteriosus becoming obliterated (after Dalton).
Fig. 7.—Shows human foetal and adult hearts.
A. Heart of fcetus at the end of the sixth month, a, Inferior vena cava ; h, superior vena cava ; c, cavity of the right auricle,
laid open in front ; d, auricular appendix ; e, cavity of the right ventricle, also laid open ; /, Eustachian valve. The arrow placed in
the inferior vena cava passes behind the Eustachian valve, crosses the cavity of the right auricle, and passes through the foramen
ovale to the left auricle.
B. Indicates the course of the blood through the adult heart {vide darts), a, a, Vena cava, superior and inferior ; b, right
ventricle ; (, pulmonary artery ; d., pulmonary vein ; e, left ventricle ; /, aorta (after Dalton).