498 THE HORSE. 



and a consequen;; movement of the bones to which they are 

 attached. The brain may be compared to a telegraph operator, 

 the spinal cord to his galvanic battery, and the nerves to the 

 wires. A chicken with its head off kicks and flutters with strength 

 enough to fly over a barn, or to run around it. The spinal cord 

 generates the power for a short time, and would do so longer but 

 for the loss of blood; but the brain, that gives intelligent direc- 

 tion to the power, is not there. The battery is sending its elec- 

 tricity along the wires without the control of the operator. 



If enough of the nerve force is sent to the muscles to move the 

 body a mile in six minutes, it is six minutes in being generated. 

 If the same amount of nerve force can be generated and sent to 

 the muscles in three minutes, we might suppose that the body 

 would be moved the same distance in three minutes 3 and herein 

 would appear to lie all the difference of speed. But the amount 

 of force generated by the nervous centre, and expended by the 

 muscles, in a given time, does not exactly explain the difference 

 of speed. One horse may expend as much nerve force in pulling 

 a load a quarter of a mile in three minutes, as another does in 

 trotting a whole mile in the same time, and yet not be able to trot 

 a mile in four minutes. The speed depends on the ability of the 

 spinal cord to generate and send to the different sets of muscles 

 concerned in locomotion, the required amounts of nerve force in a 

 quick succession of discharges ; and on the capability of the nerves 

 to transmit it to the muscles in large quantity in a short time. 

 The difference between trotting fast and drawing a heavy load, is 

 not in the amount of force used, but in the manner of using it. 

 In one case, the nerve force is sent to a muscle during the whole 

 time of taking a slow step with a heavy load ; and in the other, it 

 is all expended in an instant, causing the muscle to contract 

 quickly, and thereby projecting the horse rapidly forward — the 

 acquired momentum continuing after the muscle ceases to con- 

 tract. It is like driving a nail by a succession of blows, that 

 could not be moved by the same aggregate amount of pressure dif- 

 fused and continued over the whole time of driving. 



The essential quality of speed, at any gait, is therefore a cer- 

 tain organization of the nr-vous system, and this is the one thing 

 needful in every case. This is what we breed for when we breed 

 for speed; this is the quality that has been transmitted through 

 so many generations from Messenger, Diomed, Pilot, Bellfounder, 

 and other progenitors of American trotters. A descendant of 

 Messenger might have neither his form, size, nor way of going, 

 but if he had a similar organization of the nervous system, he 

 would have speed. We cannot detect this peculiarity of organiza- 

 tion by any outward sign ; we can know of it only by its mani- 

 festations. We know that it is hereditary, and we also know that 



