English: Fig 3—A. Dissection and photograph by Pettigrew (1860) of the apex of the left ventricle of the heart of the sheep. Preserved in the Anatomical Museum of the University of Edinburgh .Shows beautiful right-handed symmetrical spiral whorl composed of two sets of muscular fibres (a, b) which wind into the interior of the ventricle as indicated by the darts.
B. Plaster of Paris cast by Pettigrew (1876) of the right and left ventricular cavities of the human heart. Preserved in the Museum of the Royal College of Surgeons of England. Shows fine left-handed symmetrical spiral composed of two parts (a,b). In this case the spiral runs from the apex to the base of the ventricles (vide darts), which is the opposite of A, where the spiral runs from the base to the apex. Compare with spiral nebulae; spiral flowers;spiral seeds; and spiral shell.
Fig.4.— Diagram by the Pettigrew (1859), showing that external and internal muscular fibres of the left ventricle of the heart are arranged spirally, and form two sets of left and two sets of right-handed spirals: that the two sets of external fibres which constitute the left-handed spirals involute and enter the apex and become continuous with the two sets of internal fibres constituting the right-handed spirals, which latter in turn evolute at the base and become continuous with the two sets of spiral external fibres as indicated by the arrows and the numerals 1, 2, 3, 4, 5, 6, 7, 8, 9, 10.