608 THE BOOK OF THE DOG. 



we have done all that space will permit, and must now describe a few of the more common 

 disorders of the nervous system. 



First, however, just one word on what is called reflex action, the simplest example of which 

 probably is the act of deglutition. The throwing a morsel of food backward towards the pharynx 

 by means of the tongue is a voluntary action, but when the morsel has reached the top part 

 of the pharynx, and tickles or excites the lining membrane, the action of swallowing is no longer 

 under our control, for the excitement is carried by one set of nerves to the top of the spinal 

 cord, induces there a motor-power which is transmitted along another set of nerves to the muscles 

 of the pharynx, and thus the act is completed, and would be even if the power of the brain 

 were destroyed, as in apoplexy. 



The diseases of the nervous system of the dog, as at present understood, are by no means 

 numerous, comprehending only paralysis, fits, inflammation of the brain, chorea, and asthma. 

 Some writers include rabies in the list of nervous ailments. It should not be so included. However 

 much the nervous system may suffer in rabies (or hydrophobia), it is clearly a disorder depending 

 upon a morbid condition of the blood, caused by a specific poison. 



I. Paralysis. 



If the diseases of the nervous system are difficult to treat, and even difficult of intelligible 

 comprehension in the human being, much more so are they in the lower animals, who can 

 neither speak nor tell their feelings. Our treatment of these ailments in the dog must often 

 be, to a great extent, speculative and empirical. Nervous diseases are not yet understood by 

 the medical profession ; our theory of causation is often at fault. Could we even manage to 

 ascertain the physical conditions in a diseased brain or spinal cord, it would remove at least 

 a portion of our difficulties ; but they are hidden away from us under their bony shields, and we 

 can only guess at their state and condition from the symptoms in other parts of the body, and 

 these are often most deceptive. We find one day a certain train of symptoms, which after death 

 and dissection we attribute to a certain condition of the brain or spinal marrow ; we find another 

 day the same train of symptoms in another case, and, behold ! a post-mortem reveals to us not 

 the same, but quite a different alteration in the nerve-centres. Another difficulty is that we 

 are often unable to tell whether the symptoms of interference with the natural functions of the 

 nerves which we see before us are due to a lesion in the nerves themselves or their centres, 

 or whether they are merely sympathetic, and dependent upon disease or disorder in some other 

 part of the body 1 



The symptoms of paralysis or loss of power in a limb or in any group of muscles are familiar 

 to every one. In a paralysed limb there is either entire or partial loss of power. It may arise 

 from pressure on the roots of the nerve, pressure by effusion or otherwise upon the spinal cord 

 or brain itself, from a diseased or altered condition of the component parts of the great 

 nerve-centres, and it may arise from constipation in the case of the hind-quarters. In cases 

 of facial paralysis, one side of the face only is paralysed. The symptoms are caused by some 

 pressure upon or disease of the seventh pair of nerves. In this case there will be difficulty of 

 mastication on the paralysed side, and constant dribbling away of saliva from the pendant lips. 



Paralysis is sometimes the result of a blow or injury to the spinal column, causing either the 

 fracture or displacement of a bone, or simple congestion. These cases may prove speedily fatal 

 or get slowly well, according to the extent of the injury. 



Another cause of paralysis, which we sometimes see in puppies, is caused by the irritation 

 of teething about the fourth or sixth month or indigestion, and want of sufficient exercise. 



