"In the second place, to penetrate completely the natural reason of the proportions of the human body, would require a knowledge of physics, which it is not in man's power to obtain. The universal equilibrium of the numerous constituent parts of the human machine, every one of which eminently attains the end for which it was destined, without interrupting the course that every other part takes to its respective end, in which true proportion seems to consist, is more easily stated than understood. And even if an artist could arrive at such a knowledge of man as to be able, so to speak, to compose him, he would have done but little, because he would have made but one man. By the alteration of only one of the infinite parts that compose the human frame, the equilibrium and respective relation of the others are necessarily altered: in short, each separate individual would be the subject of a totally new study. "Every human habit, of whatever nature it may be, has an influence over the human figure, and from the indefinable variety and incalculable mixture of such habits, there results an infinite variety of figures. Thus, it is evident that true general proportions cannot be laid down without violating nature, which it is the object of art to imitate."--If, by "general proportions," Bossi here means proportions applicable to all or to a great number, he completely loses sight of the object of the great man on whose opinions he comments; for he sought _a rule for the harmony of parts in each distinct individual_! Again, Bossi abandons, as impossible, the finding of the harmonic rule, which was the great object of Leonardo.--"From what has been said, we may finally conclude that large proportions only can be established, and that placing too much confidence in measures, retards, rather than favors the arts. "It was written of Raphael, and is seen, that he had as many proportions as he made figures. Michael Angelo did the same, and it was his saying, that he who had not the compasses in his eye, would never be able to supply the deficiency by artificial means. Vincentio Danti, who treasured the doctrine of Michael Angelo, asserts in his work, that the proportions do not fall under any measure of quantity. We have seen the infinite exceptions of Leonardo, respecting the measurement of man, and his own few works confirm it. I speak no more of inferior persons among the moderns; but turning to the ancients, I find that the proportions of every good statue are different."--And this will be found conformable to the harmonic rule. "And speaking generally of works in relievo, what canons can determine the largeness or smallness of some parts, so as to obtain a greater effect according to the circumstances of light, distance, material, visual point, &c.? Certainly none."--This was not to be expected from the rule sought for.