30 OUTLINES OF ANATOMY IN THE HORSE. 



the influence of the will, are said to have a mixed motion. 

 If we examine the fibres of muscles attentively, we find them 

 not in straight, but in zigzag lines, which explains how they 

 are able to contract and expand. These fibres may be divid- 

 ed and subdivided, until they are too small for the naked eye 

 to see ; they are then called fascia, and these fascia are again 

 united to form muscle. In a work of this description, which 

 is intended for the non-professional, the author deems it un- 

 necessary to detail the names of the different muscles, which 

 would involve an amount of matter incompatible with the 

 present limits. Suffice it to say, that the names of the vol- 

 untary muscles depend on their size, form, use, the arrange- 

 ment of their fibres, or their origin and insertion. 



Nerves are long, firm, white cords, which ramify after the 

 manner of blood-vessels, and are distributed to all parts of the 

 animal. They issue from the brain, medulla oblongata, and 

 spinal marrow. They consist of fascicula, or bundles of dis- 

 tinct fibres, closely connected together, and covered with a 

 membrane called neurilema. They divide into branches, 

 twigs, and threads, which again subdivide into filaments.. 

 They are named from their origin, use, and form. Thus 

 those that issue from the brain are called cerebral; others, 

 again, from the spinal cord, are called spinal ; those in the 

 region of the neck are called cervical; others, issuing from 

 other parts of the spinal column towards the extremities, are 

 called lumbar, dorsal, and sacral. These names correspond 

 to their locations. See Nerves, part second. 



If a nervous cord is cut through, as in nerving, or com- 

 pressed with force, so as to intercept all communication with 

 the brain, and the foot to which it is distributed, that part 

 becomes paralyzed. In nerving horses or cattle, the sensi- 

 bility of the foot is wholly or partly destroyed, according to 

 the nature of the operation. 



Veins are the vessels that return the blood to the heart. 

 The texture of veins is much more slender than that of 

 arteries, yet they possess considerable strength, and though 

 sometimes distended to their utmost capacity, seldom burst. 



