280 MANUAL OF EQUINE MEDICINE. 



with sensory functions. These fibres pass through the 

 tegmentum of the crus, and thence along the sensory tracts 

 of the medulla and cord. 



The motor fibres, on reaching the medulla oblongata, 

 decussate or cross over to the opposite side, pass down the 

 anterior and lateral columns of the cord, and emerge by 

 the anterior roots of the spinal nerves. The sensory 

 fibres enter the cord by the posterior roots of the spinal 

 nerves, cross immediately to the opposite side, thence pass 

 upwards to the medulla, and onwards in the way above 

 indicated. 



If, therefore, one half of the cord below the medulla be 

 destroyed, loss of motion on the same side as the lesion and 

 loss of sensation on the opposite side, would follow. 

 Destruction of one half of the brain would cause loss of 

 motion and sensation on the opposite side to that of the 

 lesion. Pathological observation and recent experimental 

 researches have shown that combined movements uniformly 

 follow excitation of certain areas of the cortical surface, and 

 that destructive lesion of the same parts is followed by 

 paralysis of special groups of muscles. But for further 

 particulars of these special centres we must refer the reader 

 to Dr. Ferrier ' On the Functions of the Brain,' or to Dr. 

 Foster's * Physiology,' in which a very clear account of the 

 localization of cerebral functions is fully given. 



Seeing that the structure of the brain is far less complex 

 in the horse than in man, and that it forms, as the following 

 table of Colin will show, a much lower proportion to the rest 

 of the body, diseases of the nervous apparatus are of far 

 less frequent occurrence in the equine species than in our 

 selves. 



