2 DISEASES OF THE BRAIN AND NERVES. 



as, in a man, indigestion may cause headache, or a blow upon the 

 stomach excite sickness, and even death ; so, in a horse, an over- 

 loaded stomach may give rise to a cerebral disorder, well known to 

 veterinarians and others by the designation " stomach-staggers* :" 

 the symptoms of which sometimes so nearly resemble those of 

 organic disease of the brain itself, that, but for the history attached 

 to them, the seat of disease might be altogether mistaken. 



Traumatic tetanus is another example of functional derangement 

 and reflex nervous irritation : a horse receives a prick in one of 

 his feet from a nail, and locked-jaw is the consequence of it. 



On the diseases of the brain and nerves, and their effects on the 

 different organs and structures of the body, the late successful in- 

 vestigations into the anatomy and physiology of the nervous sys- 

 tem have cast lights, enabling us very much better to comprehend 

 their nature, and directing us to a more defined and rational mode 

 of practice. We now know for certain, that the cerebrum is the 

 seat of sensation and volition, the source of what intuitive reason 

 or sagacity the animal possesses ; and, consequentlj', that any im- 

 pairment of these functions is to be imputed to disease or derange- 

 ment of, or reflected upon, that division of the brain. The spinal 

 marrow being in reality but a process or continuation of the cere- 

 brum, sensation and volition are conveyed to and from the cere- 

 brum through that body, the same as those impressions would be 

 through the medium or intervention of any large nervous trunk. 

 Removal or destruction of the cerebrum annihilates all sensation 

 and voluntary power, but not, immediately or consequently, or- 

 ganic life ; for signs of that are still demonstrable in the brainless 

 body, even in the highest orders of animals ; though this remnant 

 of vitality is supportable only for a time : one, and that the grand 

 system — the primum mobile — being destroyed, the others are un- 

 able of themselves to carry on the functions necessary to the con- 

 tinuance of the vital property. Section or injury of the spinal 

 marrow will only deprive of sensation and motion such parts as 

 derive their nerves from it below the part divided, injured, or com- 

 pressed ; the same as division or compression of a nerve affects 



* Described in section x, vol. ii, page 195. 



