QUESTIONS AND ANSWERS 73 



"H"), called the commissure, which shows in its middle the central 

 canal of the cord. 



The cord is traversed throughout its length by two fissures, the 

 superior of which is narrower and shallower than the inferior, which 

 is only separated from the gray commissure by a white band, the 

 white commissure. 



The white matter is divided on each side into three columns. The 

 superior column lies between the superior fissure and the superior 

 or sensory nerve root. The inferior, between the inferior fissure 

 and the inferior or motor root. The lateral lies between the two. 

 The cord is covered by membranes similar to the braia, viz., dura 

 mater, arachnoid and pia mater. The posterior end of the cord 

 is marked by a narrow prolongation, the flum terminate. 



Describe the spinal nerves. 



The spinal nerves emanate from the spinal cord and leave the 

 vertebral canal by the intervertebral foramina to proceed to the 

 various organs. They proceed from the lateral aspects of the cord 

 by two orders of roots : one motor, the other sensitive. These two 

 roots unite into a very short trunk in passing through the inter- 

 vertebral foramen and this mixed nerve divides almost immediately 

 into two terminal branches. On the superior root, before its union 

 with the inferior, a ganglion is found. Passing out with the in- 

 ferior root of the spinal nerve, but indistinguishable from it, is a 

 branch of nerve known as the white ramus communicans which 

 leaves the main trunk aftet the mixed nerve has been formed, and 

 runs to a distinct system known as the sympathetic. 



How many pairs of spinal nerves are there in the horse? State the 



relative number in the cervical, dorsal, lumbar, sacral and 



coccygeal regions, respectively. 



There are 42 or 43 pairs of spinal nerves as follows: cervical, 



8 pairs; dorsal, 17 pairs; lumbar, 6 pairs; sacral, 5 pairs; and 



coccygeal, 6 to 7 pairs. 



Name the cranial nerves. 



Olfactory, optic, motor oeuli, patheticum, trifacial, abducens, 

 facial, auditory, glossopharyngeal, pneumogastric, spinal accessory 

 and hypoglossal. 



Describe the first pair of cranial nerves. 



The olfactory nerves originate, superficially, in the olfactory 

 lobe of the brain, deeply, from the corpus striatum and transverse 

 fibres of the pons. Pass through the cribriform plate of the ethmoid 

 bone and are widely distributed over the nasal septum and ethmoidal 



