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, um- 

 bilical 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). 



