256 THE VITAL FUNCTIONS. 



been in danger of being compressed by the violent 

 contractions of the muscles : to guard against this 

 inconvenience, it is made to pass through a per- 

 foration in the bone itself, where it is completely 

 secure from pressure.* In like manner the coffin 

 bone of the Horse is perforated for the safe con- 

 veyance of the arteries going to the foot. 



The energy of every function is regulated in a 

 great measure by the quantity of blood which the or- 

 gans exercising that function receive. The muscles 

 employed in the most vigorous actions are always 

 found to receive the largest share of blood. It is 

 commonly observed that the right fore leg of qua- 

 drupeds, as well as the right arm in man, is stronger 

 than the left. Much of this superior strength is, 

 no doubt, the result of education ; the right arm 

 being habitually more used than the left. But still 

 the different mode in which the arteries are distri- 

 buted to the two arms constitutes a natural source 

 of inequality. The artery supplying the right arm 

 with blood is conjoined at its origin with the artery 

 conveying blood to that side of the head, and pro- 

 ceeds in a more direct course from the heart than 

 the artery of the left arm, which arises separately, 

 and at a greater distance from the heart than even 

 the artery going to the left side of the head. Hence 

 it has been inferred that the right arm is originally 

 better supplied with nourishment than the left. It 

 may be alleged, in confirmation of this view, that 



* The brachial artery passes, in hke manner, through a foramen 

 in the inner condyle of the humerus, in many species of Quadru- 

 mana, Carnivora and Rodentia ; this protection appearing to have 

 been given to those tribes more especially, which are endowed with 

 great freedom of action in tlie fore limbs. 



