Chapter 12

The brain, spinal cord, and the ganglia are the central organs of the nervous system. The nerves conduct the nervous influence. The nerves terminate differently according to their function. The terminations are called end organs. The terminal end organs in the skin and other parts endowed with sensation receive the impressions, which are conveyed to the brain, where they are appreciated. They are so sensitive that the most gentle zephyr is perceived. They are so abundant that the point of the finest needle can not pierce the skin without coming in contact with them, and the sensation of pain is instantly conveyed to the brain. The terminal end organs of the nerves that supply the muscles are different, as they give the impulse which is conveyed by the motor nerves to the elements which constitute the muscle, and this impulse is the excitation which causes the muscle to contract. The terminal end organs of the special senses of taste, smell, etc., receive their special impressions, and their respective nerves carry the impressions to the brain.

There are two divisions of nerves, the afferent and efferent.

The afferent nerves are those which convey the impression to the nerve centers. All the sensory nerves belong to this division.

The efferent nerves are those which convey the nervous impulse outward from the nerve centers, and they are further classified according to the function of their respective centers. For example: Motor fibers carry the impulse from the nerve center to a muscle to cause contraction. Vasomotor fibers carry the impulse to the muscular tissue in the blood vessels, which regulates their caliber. The secretory fibers convey the impulse to the cells of the glands and excite the activity of the gland, and its particular product is secreted or evolved, as, for instance, milk in the mammary gland. Inhibitory fibers control or inhibit the action of the organ to which they are distributed, as, for instance, the heart.

Nerve centers may be considered as a collection or group of nerve cells. Both the cerebrospinal and the sympathetic divisions have nerve centers. The centers derive their special names from their functions. The brain is the great center of the nervous system, as it is the center of intelligence and perception. The centers of all the special senses, as well as the centers of various functions, are located in different parts of the brain. Nerve centers also exist in the spinal cord and in connection with the sympathetic system.

A nerve is a cord consisting of a certain number of fibers of nerve tissue, inclosed in a sheath of connective tissue. Nerves divide and subdivide, sending off branches, which ramify in all parts of the body, and, as they near their terminations, they contain but one or two fibers.

The brain and spinal cord are contained within a bony canal, which forms a protective covering for them.

The spinal cord, or spinal marrow, lodged within the spinal canal, or hollow of the backbone, is continuous with the brain anteriorly, and terminates in a point in the sacrum (that part of the spinal column which immediately precedes the tail). The spinal cord gives off branches at each of the spaces between the segments of the backbone. These branches form nerve trunks which carry both sensory and motor impressions and impulses. The spinal cord is a grand nerve trunk to carry messages to or from the brain and to and from the reflex centers contained within itself.

The brain is contained within the cavity of the skull and is continuous with the spinal cord; there is nothing to mark the place where one leaves off and the other begins. The brain is the seat of reason and intelligence. Voluntary effort originates from the brain. Coordination, or harmony of movement, is controlled by the rear portion of the brain, known as the cerebellum.

The meninges are the membranes, three in number, which envelop the brain and spinal cord, and separate them from the bones which form the walls of the cranial cavity and spinal canal.

The sympathetic, also called the ganglionic, division of the nervous system consists of two chains of ganglia, reaching from the head to the tail, situated beneath the spinal column, one on either side. The presence of the ganglia or enlargements on the cords give them their chainlike appearance.

The sympathetic nerves are closely connected with the cerebrospinal nerves, but are not under the control of the will.

INFLAMMATION OF THE BRAIN AND ITS MEMBRANES (STAGGERS).

Inflammation of the brain is technically termed encephalitis and of its membranes cerebral-meningitis, but as both conditions usually occur together, and since it is practically impossible to distinguish one from the other by the symptoms shown by the diseased animal, they may as well be considered together here as varieties of the same disease. Staggers, coma, frenzy, etc., are terms that are sometimes applied to this disease in its different forms or stages.

_Causes._--Severe blows on the head with a hard object, or the head coming violently in contact with the ground or other hard substance in a fall, may be followed by encephalitis. Irritation caused by tumors in the brain may produce inflammation. Feed containing deleterious matters--for example, ergot (see Pl. V) and other fungi which contain a narcotic principle--is the most frequent cause of this affection, and hence it is often called "grass staggers" and "stomach staggers." Highly nitrogenous feeds are blamed for causing this disease. Parasites, mineral and narcotic poisons, hot weather, and severe exertion or excessive excitement may cause this condition. Inflammation of the brain may occur as a complication of some infectious disease or may follow some forms of indigestion. In many localities certain plants have the reputation of causing staggers.

_Symptoms._--The symptoms vary much, but a careful observer will detect a trouble connected with the nervous system without much uncertainty. The first signs may be those of frenzy, but generally at the start the animal is dull and sleepy, with little or no inclination to move about; the head may be pressed against the wall or fence and the legs kept moving, as if the animal were endeavoring to walk through the obstruction; the body, especially the hind part, may be leaned against the side of the stall or stable, as if for support. The bowels are constipated; the urine, when passed, is small in quantity and darker in color than natural. There may be trembling and even spasms of muscles in different parts. In the dull stage the animal may breathe less frequently than is natural, and each breath may be accompanied with a snoring-like sound. The pulse may be large and less frequent than normal. If suddenly aroused from the drowsy state, the animal appears startled and stares wildly. When moving about it may stagger, the hind quarters swaying from side to side.

If delirium ensues, the cow is commonly said to be mad. She may bellow, stamp her feet, run about wildly, grate the teeth, froth at the mouth. If she is confined in the stable, she rears and plunges; the convulsions are so violent in many instances that it is really dangerous for one to attempt to render aid. The body may be covered with perspiration. She may fall; the muscles twitch and jerk; often the head is raised and then dashed against the ground until blood issues from the nose and mouth; the eyes may be bloodshot and sightless; the limbs stiff and outstretched, or they may be kicked about recklessly; the head may be drawn back and the tail drawn up; the urine may be squirted out in spurts; often the "washer" (membrane nictitans) is forced over the eye. When the convulsions cease they may be followed by a period of quiet unconsciousness (coma) which is more or less prolonged, when the animal may gradually regain consciousness, get up on its feet, and perhaps quietly partake of food, if there be any within reach, while at other times it arises with much difficulty and staggers blindly about the stall or field.

It must be remembered that all the foregoing symptoms are not always seen in the same case. In those cases usually designated "sleepy staggers" the general symptoms of drowsiness are presented, while in other cases the symptoms of frenzy cause the affection to be called "mad staggers." In other cases there are symptoms of paralysis, swaying of the hind quarters, inability to rise, etc., and sometimes these symptoms of paralysis are the most striking manifestations and continue until death. Acute cases are accompanied by fever.

It is well to remark that when the disease follows injuries to the head the symptoms may not be manifested until two or three days (or longer) after the accident.

_Treatment._--Recoveries are rare in spite of careful attention. To be of any service whatever the treatment must be prompt and begin with the disease. In the early stage, when the pulse is large, most cases will admit of bleeding. Eight or 9 quarts of blood should be taken from the jugular vein. This should be followed immediately by a purgative, the following for a cow of average size: Epsom salt, 24 ounces; pulverized gamboge, one-half ounce; croton oil, 20 drops; warm water, 3 quarts; mix all together and give at once as a drench. About 2 quarts of warm water or warm soapsuds should be injected with a syringe into the rectum every three or four hours. It is best to keep the animal in a quiet, sheltered place, where it will be free from noise or other cause of excitement. All the cold water the animal will drink should be allowed, but feed must be withheld, except bran slops occasionally in small quantities, or grass, if in season, which may be cut and carried fresh to the patient.

The skull must be examined, and if sign of injury is found, appropriate surgical treatment should be given.

During the convulsions all possible efforts should be made to prevent the animal injuring itself. The head should be held down on the ground and straw kept under it. Cold water may be continuously poured on the head, or bags filled with ice broken in small pieces may be applied to the head. Different authors recommend different remedies to allay the convulsions, but for two reasons it will be found extremely difficult to administer medicines during the convulsions: (1) While the animal is unconscious the power to swallow is lost, and therefore the medicine is more liable to go down the windpipe to the lungs than it is to go to the paunch; (2) the convulsions are often so violent that it would be utterly useless to attempt to drench the animal; and furthermore it must be borne in mind that during this stage the functions of digestion and absorption are suspended, and as a consequence the medicine (provided it finds its way to the paunch) is likely to remain there unabsorbed and therefore useless.

A blistering compound, composed of mustard, 1 ounce; pulverized cantharides, one-half ounce; hot water, 4 ounces, well mixed together, may be rubbed in over the loins, along the spine, and back of the head on each side of the neck. This is occasionally attended with beneficial effect, and especially so in those cases when paralysis is present.

If the purgative acts and the animal shows signs of improvement in the course of two or three days, 2 drams of iodid of potassium may be given every night and morning, dissolved in a half bucketful of drinking water, if the animal will drink it, or it may be dissolved in a half pint of water and given as a drench. Great care must be observed in regard to the food, which should be nutritive, but not coarse, and at first in small quantities, gradually increased as the patient improves. After some progress is made toward recovery 1-1/2 drams of pulverized nux vomica may be given twice a day, added to the iodid of potassium drench. This should be administered so long as a staggering gait continues.

In those rare cases when recovery takes place it is only partial as a rule, as there is generally a sequel which remains, such as partial paralysis. However, this is but a slight drawback in cattle, because when it is seen to persist the medicine should be stopped and the animal fattened for butchering.

Post-mortem examinations discover congestion of the brain and its membranes. In those cases which have exhibited much paralysis of the hind legs before death the cord may be congested in the lumbar region (loins). When the disease has been caused by injury to the head, the congestion and extravasated blood may be found inside of the cavity in the location corresponding to the place where the injury was inflicted externally. In some cases pus is also discovered. It remains to be said that in all animals that have died from this affection the lungs are found very much congested. This may lead the superficial observer to suppose that the disease was a lung affection, but in fact it is only a natural consequence when death ensues from brain disease.

APOPLEXY.

That form of congestion of the brain known as parturient apoplexy, or parturient paresis, which is so frequently associated with the period of calving is described in another part of this work. (See "Milk fever," p. 226.)

Cerebral apoplexy, not connected with parturition, is a rare disease among cattle. However, it may be due to degeneration and consequent rupture of a blood vessel in the brain.

The attack is sudden, the animal in most cases falling as if it had received a blow on the head. It may stagger and reel some time before going down. After falling, there are convulsive movements of the legs or the animal sinks into insensibility. There may be remissions in the severity of the symptoms, but the pressure from the continued escape of blood soon causes death. Rest, quiet, friction to the legs and surface, frequent turning of the animal and cold to the head are to be practiced, if treatment is attempted.

CONGESTION OF THE BRAIN.

There is a form of congestive apoplexy affecting cattle which are in a plethoric condition. The congestion, or overfilling with blood, causes pressure on the brain substance and disorganizes its function. It occurs mostly in hot weather. In this disease the symptoms are somewhat similar to those exhibited when the animal has encephalitis, but the onset is more sudden, the duration is shorter, and there is less fever. There may be frenzy or coma, or alternations one with the other. The intelligence is diminished, staring eyes, bracing with the legs, pressing against the stall partition or manger, red mucous membranes. This condition usually terminates in recovery.

In such cases bleeding should be resorted to immediately, and when the power of swallowing is not lost purgatives should be administered. Cold applications to the head and the general treatment recommended for encephalitis are indicated.

CONCUSSION OF THE BRAIN.

Severe blows on the head, striking the head against some hard object while running, or falling on the head may cause concussion of the brain. The injury may fracture bones of the cranium and produce compression of the brain.

_Symptoms and treatment._--The symptoms and the treatment that is indicated differ very little from what has been said under congestion of the brain and under encephalitis. In some cases it may be necessary to operate to remove a piece of bone that is pressing on the brain or to remove a clot of blood under the area which received the blow.

EPILEPSY.

This affection is characterized by the occurrence of sudden convulsions. The animal may appear to be in a fair state of health usually, but at any time, in the stable or in the field, it may have a convulsion in which it will fall and lose consciousness. Epilepsy must not be confounded with vertigo--the fainting which is an effect of heart troubles.

The exact cause of epilepsy in the majority of cases is unknown. Post-mortem examinations in many instances have failed to discover any lesion in connection with the brain or nervous system, while in other instances disease of the brain has been found in the form of thickening of the membranes, abscesses, and tumors, and in some cases the affection has been manifested in connection with a diseased condition of the blood. The cause has also been traced to reflex irritation, due to teething, worms, and chronic indigestion.

_Treatment._--When the affection is due to the last-named causes treatment may be successful if the cause is removed. If there are symptoms of worms or of indigestion, follow the general treatment advised for those troubles under their proper heads. If due to irritation caused by teething, the inflamed gums must be lanced. Examination of the mouth often develops the fact that one of the temporary teeth causes much irritation by remaining unshed, and thereby interfering with the growth of a permanent tooth. The offending tooth should be extracted. When the cause of epilepsy can not be discovered, it must be confessed that there is no prospect of a cure. However, some benefit may be expected from the occasional administration of a purgative dose of medicine. A pound of Epsom salt dissolved in a quart of warm water, for a cow of average size, may be given as a drench once or twice a month. In addition to the purgative, 4 drams of bromid of potassium, dissolved in the drinking water, three times a day, has proved very beneficial in some cases.

SUNSTROKE (PROSTRATION FROM HEAT).

Owing to the fact that cattle are seldom put to work at which they would have to undergo severe exertion, especially in collars, they are not frequently prostrated by the extreme heat of the summer months. When at pasture they select the coolest places in the shade of trees, in water, etc., when the heat becomes oppressive, and thereby avoid, as much as possible, the effects of it.

It does happen, however, that cattle that have been kept up for the purpose of fattening, when driven some distance in very hot weather, are sometimes prostrated, but it must be remembered that it is not really necessary for the animal to be exposed to the rays of the sun, as those confined in hot, close places may suffer. This often happens in shipping, when they are crowded together in cars.

_Symptoms._--The premonitory signs are those of exhaustion--dullness, panting, frothing at the mouth, tongue hanging out, irregular gait, uneasiness, palpitation--when, if the circumstances which tend to the prostration are not mitigated, the animal staggers or sways from side to side, falls, struggles for a while, and then gradually becomes quiet, or the struggles may continue, with repeated but ineffectual efforts to regain a standing position. In serious cases the attack may be very sudden, unconsciousness occurring without continued or distressing premonitory symptoms.

_Treatment._--At first, when not very serious, removal to a quiet, sheltered place, with a few days on a reduced diet, is all that need be done. When the animal has fallen, apply cold water or ice to the head; rub the body and limbs with cloths or wisps of straw and continue the rubbing for a considerable time. If the power of swallowing is not lost (which may be ascertained by pouring a little cold water into the mouth), give 3 drams of stronger liquor ammonia, diluted with a quart of cold water. Be very careful in drenching the animal when lying down. Repeat the drench in a half hour and an hour after the first one has been given. Instead of the ammonia, a drench composed of 3 ounces of spirits of nitrous ether in a pint of water may be given, if more convenient, but the ammonia drench is preferable. If unconsciousness continues, so that a drench can not be administered, the same quantity of ammonia and water may be injected with a syringe into the rectum. The popular aqua ammonia, commonly called "hartshorn," will do as well as the stronger liquor ammonia, but as it is weaker than the latter the dose for a cow is about 1-1/2 ounces, which should be diluted with a quart of water before it is given to the animal, either as a drench or an enema. When ammonia can not be obtained, an ounce of tincture of digitalis may be given.

As soon as the animal is able to rise it should be assisted and moved to the nearest shelter. All the cold water it will drink should be allowed. The ammonia or spirits of nitrous ether drench should be administered every three hours so long as there is much failure of strength. The diet should be limited for several days--bran slops and a little grass. When signs of returning strength are presented, 12 ounces of Epsom salt dissolved in a quart of warm water may be given in those cases which have been down and unconscious, but do not give it while much weakness remains, which may be for several days after the attack. The flesh of an animal that is suffering from heat stroke should not be prepared for use as food. On account of the fever with which the animal suffers, the flesh contains toxins that may render it poisonous to the consumer.

INJURIES TO THE SPINAL CORD.

The spinal cord is liable to concussion from blows and falls, and paralysis, to a greater or less extent, may be the result. Fracture, with displacement of the bones (vertebrÊ) which form the spinal column, by compressing the spinal cord, produces paralysis, which varies in its effect according to the part of the cord that is compressed. If the fracture is above the middle of the neck, death soon follows, as communication between the brain and diaphragm (the essential muscle of inspiration) is stopped. When the fracture is farther down in the neck, posterior to the origin of the phrenic nerve, the breathing continues, but there is paralysis in all parts posterior to the fracture, including the fore and hind legs. When the fracture is in the region of the loins the hind legs are paralyzed, but the fore legs are not. If the fracture is in the sacrum (the division of the spinal column between the loins and the tail), the tail alone is paralyzed.

As a matter of course, when the back is broken there is no remedy; the animal should be killed at once.

PARALYSIS.

Paralysis, or loss of motion in a part, may be due to a lesion of the brain, of the spinal cord, or of a nerve. It may also be caused by reflex irritation. When the paralysis affects both sides of the body, posterior to a point, it is further designated by the name paraplegia. When one side of the body (a lateral half) is paralyzed, the term hemiplegia is applied to the affection. When paralysis is caused by a lesion of a nerve, the paralysis is confined to the particular part supplied by the affected nerve.

As already pointed out, paralysis may be due to concussion of the spine, fracture of a bone of the spinal column with consequent compression of the spinal cord, concussion of the brain, or compression of the brain. An injury to one side of the brain may produce paralysis of the same side of the head and of the opposite side of the body (hemiplegia). Paralysis may occur in connection with parturient apoplexy, lead poisoning, ergotism, etc.

CONGESTION OF THE SPINAL CORD.

Paraplegia, or paralysis of the rear part of the body, is the dominant symptom in congestion or inflammation of the spinal cord. The cause is not known, but the disease is probably due to chilling. It is thought by some that some toxic influence (poison) may be responsible for its development.