Secondly, The grounds and reasons alleadged for the right, are not satisfactory, and afford no rest in their decision. _Scaliger_ finding a defect in the reason of _Aristotle_, introduceth one of no less deficiency himself; _Ratio materialis_ (saith he) _sanguinis crassitudo simul et multitudo_; that is, the reason of the vigour of this side, is the crassitude and plenty of blood; but this is not sufficient; for the crassitude or thickness of blood affordeth no reason why one arm should be enabled before the other, and the plenty thereof, why both not enabled equally. _Fallopius_ is of another conceit, deducing the reason from the Azygos or _vena sine pari_, a large and considerable vein arising out of the _cava_ or hollow vein, before it enters the right ventricle of the Heart, and placed only in the right side. But neither is this perswasory; for the Azygos communicates no branches unto the arms or legs on either side, but disperseth into the Ribs on both, and in its descent doth furnish the left Emulgent with one vein, and the first vein of the loins on the right side with another; which manner of derivation doth not confer a peculiar addition unto either. _Cælius Rodiginus_ undertaking to give a reason of Ambidexters and _Left-handed_ Men, delivereth a third opinion: Men, saith he, are Ambidexters, and use both _Hands_ alike, when the heat of the Heart doth plentifully disperse into the left side, and that of the Liver into the right, and the spleen be also much dilated; but Men are _Left-handed_ when ever it happeneth that the Heart and Liver are seated on the left-side; or when the Liver is on the right side, yet so obducted and covered with thick skins, that it cannot diffuse its vertue into the right. Which reasons are no way satisfactory; for herein the spleen is injustly introduced to invigorate the sinister side, which being dilated it would rather infirm and debilitate. As for any tunicles or skins which should hinder the Liver from enabling dextral parts; we must not conceive it diffuseth its vertue by meer irradiation, but by its veins and proper vessels, which common skins and teguments cannot impede. And for the seat of the Heart and Liver in one side, whereby Men become _Left-handed_, it happeneth too rarely to countenance an effect so common; for the seat of the Liver on the left side is monstrous, and rarely to be met with in the observations of Physitians. Others not considering ambidextrous and _Left-handed_ Men, do totally submit unto the efficacy of the Liver; which though seated on the right side, yet by the subclavian division doth equidistantly communicate its activity unto either Arm; nor will it salve the doubts of observation; for many are _Right-handed_ whose Livers are weakly constituted, and many use the left, in whom that part is strongest; and we observe in Apes, and other animals, whose Liver is in the right, no regular prevalence therein.