File:Evolution; its nature, its evidences, and its relation to religious thought (1922) (14760058636).jpg

Identifier: evolutionitsnatu1922leco (find matches)
Title: Evolution; its nature, its evidences, and its relation to religious thought
Year: 1922 (1920s)
Authors: LeConte, Joseph, 1823-1901
Subjects: Evolution Religion
Publisher: New York, D. Appleton and company
Contributing Library: Mugar Memorial Library, Boston University
Digitizing Sponsor: Boston University

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Fig. 40.—Diagram of mammalian heart, a, aorta ; /), pulmonary artery;scuc, subclavium on each side; cc, carotids on each side. not especially acquainted with biology, that it is best toexplain it more fully. In Fig. 40 we give a mammalianheart and outgoing vessels, very slightly modified, so asto suggest the process of change. In Fig. 41 we givean ideal diagram representing the primitive aortic archesas they exist in the embryo of mammals, birds, andreptiles. It represents, also, substantially, the arches asthey exist in the mature condition in the most reptilianfishes (dipnoi) and in some sharks, except that in these 158 EVIDENCES OF THE TRUTH OF EVOLUTIOIf. the arches are of course furnished with gill-fringes. Wewill use this figure, therefore, to represent both the em-
Text Appearing After Image:
Fio. 41.—Ideal diagram representingthe primitive aortic arches (afterRathke). Fio. 42.—Modified for bird. bryonic condition of air-breathing vertebrates and themature condition of some fishes. The place of the heartis indicated by the dotted circle. Fig. 36, on page 134,shows what these arches become in reptiles (lizard). It isseen that the two upper arches on each side are obliterated,as indeed they already are in some teleost fishes. Fig. 43shows what they become in birds. The two upper archesare, of course, obliterated. The others are all modified,each in a manner which may be readily understood by PROOFS FROM EMBRYOLOGY. l.>0 comparison with Fig. 41. Finally, Fig. 43 shows what theybecome in mammals and in man. In the bird (Fig. 42)the first pair of arches become the two pulmonary arteriesas they do also in the lizard. The second pair become onthe right side (left ofthe diagram) the aorticarch, on the left side(right of the diagram)the left subclavian, sc(the right subclavi

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