106 Veterinary Elements. 



roots, one motor (the lower) the other sensitive (upper), 

 they unite and later on are combined as a mixed nerve, 

 distributing their upper fibres to the spinal muscles and 

 skin, the lower to the sides and lower parts of the trunk 

 and limbs; fibres also being sent to join the other 

 (b-or sympathetic) system. The nerves of the limbs are 

 derived from large plexuses in the armpit and groin, 

 and are generally deep-seated, accompanying the arteries 

 in their course. 



B. The sympathetic system is found underneath the 

 spinal column as two chains, with enlargements along 

 their course, as has been stated; they are the basis of 

 nerve supply to the organs of nutrition, such as the lungs, 

 liver, heart, intestines, blood vessels, etc. Surrounding 

 the brain and spinal cord are three membranes (dura 

 mater, arachnoid and pia mater), between them a fluid is 

 found, the purpose of these is to protect such sensitive 

 and important structures as the brain and cord from con- 

 cussion and injury. The proportionate size of the brain 

 and spinal cord varies in different animals according to 

 the place they occupy in the scale of intelligence; thus 

 the greater the weight of the brain the lighter the spinal 

 cord, e. #., in Man the brain weighs fifty ounces, the cord 

 one and one- half ounces; in the horse the brain weighs, 

 twenty- three ounces, the cord ten and one-half ounces; 

 the proportions respectively being 33 to 1 and 2.2 to 1. 

 The convolutions of the cerebrum are separated by de- 

 pressions (sulci), the deeper these are the higher the 

 intelligence. Captain Hayes rates the intelligence of 

 animals in the following descending scale: Man, dog, 

 cat, ass, pig, horse, ox. The nervous system of animals 



