In the year following the publication of Dr. Buchanan’s _Mechanical Theory_, Dr. John Struthers, Professor of Anatomy in the University of Aberdeen, communicated to the Edinburgh _Medical Journal_ a paper, “On the relative weight of the viscera on the two sides of the body, and on the consequent position of the centre of gravity to the right side.” In this he shows that the viscera situated on the right side of the medial line are on an average 22·75 oz. av. heavier than those on the left side. The right lung, in the male, weighs 24 oz., the left 21, giving a preponderance of 3 oz. in favour of the right. The average weight of the heart, in the male, is 11 oz. But the left side is not only the larger, but the thicker, and as the result of careful experiments by Dr. Struthers, he assigns to the right side a full third of the weight of the heart, or 3¹⁄₂ oz. for the right, and 7¹⁄₂ for the left side. Other viscera are estimated in like manner, with the result from the whole that the centre of gravity of the body, so far as it depends on their weight and position, is nearly three-tenths of an inch distant from the medial plane towards the right side. As a physical agent constantly in operation in the erect posture, Dr. Struthers states that this cannot but exert an influence on the attitudes and movements of the body and limbs; and he accordingly indicates his belief that this deviation of the centre of gravity furnishes the most probable solution of the causes “of the preference of the right hand by all nations of mankind.”