Salivary gland

“ Originally, a gland meant something in the body which was seen to make something else, generally a juice or a liquid mixture of some sort. A classical example is the salivary glands elaborating saliva. The microscope has shown us that every gland is a chemical factory in which the cells are the workers. The product of the gland work is its secretion. Thus the sweat glands of the skin secrete the perspiration as their secretion, the lachrymal glands of the eyes the tears as theirs. ”

“ Let a salivary gland be stimulated chemically, mechanically, electrically or in any other way, there always follows the same specific action—a secretion of saliva, no matter what be the kind of stimulus acting upon it, the liver-cell always reacts by producing bile, and so on. On the other hand, one and the same stimulus—the electric current, for example—gives in each form of living substance a specific result: twitching in the muscle, secretion of saliva in the salivary gland, production of bile in the liver-cell, &c. ”

“ Any acrid drug, as pyrethrum, held in the mouth acts as a sialagogue externally by stimulating the excretory ducts of the salivary glands; and the siliqua hirsuta applied externally to the parotid gland, and even hard substances in the ear, are said to have the same effect. Mastich chewed in the mouth emulges the salivary glands. ”

“ Hence a psychic event, the eager longing for food, must be accepted as an undoubted excitant of the nervous centre for the salivary glands. On the other hand, the same every-day experience, as well as numerous experiments upon animals, teach us that a number of substances, when brought into contact with the mucous membrane of the mouth, are likewise able to call forth a secretion of saliva. ”

“ Indeed, it was found that any sensory stimulus could be educated into one that would induce the flow of saliva, if the stimulus had been previously associated with food which normally excited the flow. “Any ocular stimulus, any desired sound, any odor that might be selected, and the stimulation of any part of the skin, either by mechanical means or by the application of heat or cold, have in our hands never failed to stimulate the salivary glands, although they were all of them at one time supposed to be inefficient for such a purpose. ”

“ Because the glands, which are buried in the muscles of the mouth, and which in their form are much like bunches of currants, are always full of salivary secretion. There are nerves which are distributed from the brain to these glands, and when other nerves which belong to the senses of taste, of sight, or of feeling, are excited by the presence of food, a stimulus is imparted to the salivary glands, through the nerves that surround them, their cells collapse, and the juice which they contain is poured out through their stems, or ducts, into the mouth. ”

“ Excreting glands take from an organ or from a part substances which have outlived their usefulness and are to be cast out of the body, while the secreting glands form from the blood substances that did not exist in it before, but which are of use to the body, as the ptyalin of the saliva. A strict line cannot, however, be drawn between the two kinds of glands, most glands partaking more or less of both functions, though the sebaceous and sweat glands are probably purely excreting glands and the salivary glands are almost purely secreting. ”

“ Stimulation of these fibres brings about an abundant watery secretion poor in solids. Stimulation of the sympathetic fibres system is not followed by any salivary flow, yet it has an effect on the gland, for, if after the sympathetic has been stimulated a secretion be evoked by stimulation of the glossopharyngeal nerve, the saliva secreted is very rich in organic solids. ”

“ When any solid or fluid substance is placed upon the tongue, or in contact with the inner surface of the cheeks, by an involuntary act, the salivary glands are stimulated to activity, and commence pouring the saliva into the mouth through the salivary ducts. As soon as mastication commences, the contraction of the masseter and other muscles employed in mastication stimulates the salivary glands to increased action, and a still greater quantity of saliva is secreted and forced upon the food, which is constantly being ground to a finer condition, until it is sufficiently reduced for deglutition. ”

“ Lawrie to be capable of exciting in certain constitutions an affection resembling cynanche laryngea in its symptoms, consisting of inflammation of the salivary glands, glottis, and other adjacent parts, and proving sometimes fatal. [355] This property is doubtful; but several instances have been published of profuse salivation and soreness of the mouth during a course of iodine; it is apt to cause chronic irritation of the Schneiderian membrane; and some think that it may affect in like manner the bronchial membrane in the lungs. ”

“ Even the mere thought of food will at times cause the saliva to flow, as when the appetite is stimulated by the sight or smell of some savory article; so that the common expression is correct that "the mouth waters" for the favorite articles of food. Anxiety and grief prevent its flow, and cause "the tongue to cleave to the roof of the mouth." In the horse and other animals, that feed upon dry and coarse fodder, and require an abundant supply of saliva, we find large salivary glands, as well as powerful muscles of mastication. ”

“ The emotions exert a remarkable influence upon the action of the perspiratory glands. Intense fear causes great drops of perspiration to accumulate on the skin, while the salivary glands remain inactive.
Tears. The lachrymal glands are small lobular organs, situated at the outer and upper orbit of the eye, and have from six to eight ducts, which open upon the conjunctiva, between the eyelid and its inner fold. This secretion is an alkaline, watery fluid. According to Dr. Dalton, its composition is as follows:
The function of this secretion is to preserve the brilliancy of the eye. ”

“ It is unnecessary to detail the proofs to be found in the dead body of mercurial salivation having existed during life. They are of course to be looked for in the mouth, and in the adjoining organs. We must not, however, expect to see much appearance of disease in the salivary glands; for according to Cruveilhier, in persons who die of mercurial salivation these glands do not present any trace of inflammation themselves, but merely serous effusion into the cellular tissue around them. ”

“ Glinski has instituted in the laboratory some easily performed experiments which bear upon the matter.
The experiences of daily life teach us from the outset, that the activity of the salivary glands begins even before the introduction of food into the mouth. With an empty stomach, the sight of food or even the thought of it is sufficient to set the salivary glands at once into activity ”

“ In the working of the abdominal glands nervous inhibitory processes play a large part, but they are almost wholly absent in the case of the salivary glands. This is an additional warning that one must never push the conclusions drawn from analogy too far, but must constantly bear in mind that the life-functions of all organs are extremely complicated, and that the work of even the most apparently similar organs should be submitted to separate and careful observation. ”

“ Though the secretions are not active in the fœtus, the glandular system is in general much developed. All the salivary glands and the pancreas are larger in proportion than afterwards; the liver is enormous; and the kidneys have a size much greater in proportion than they have in the adult. ”

“ The greatest number occupy places where there is constantly much motion, as the salivary glands on account of the jaw, the mucous on account of the neighbouring fleshy layer, the liver on account of the diaphragm, &c. It is this which has made it believed that this motion, foreign to their functions, was destined to produce the excretion of their fluids.195 But, 1st, the glands of the palatine arch, the pancreas, the testicles, the kidneys even, can hardly borrow accessory aid on account of their position. 2d. We know that the sight alone of grateful food makes the saliva flow. ”

“ Children scarcely ever have occasion to use their teeth. The food in use requires no chewing. Little demand is made upon the salivary glands (for food is hot, moist, and “goes down itself”) ; hence these glands, which consequently fail to develop normally, become at some time acutely diseased, or finally almost if not entirely useless. Hollow, sunken cheeks result from this cause. It was never designed to remedy this defect with fat. The parotid glands and the cheek muscles should be developed and maintained by physiological eating. ”

“ I have reason to conclude that the increased secretion of saliva is caused, not so much by the action of the chloroform on the mucous membrane of the mouth, and the extremities of the gland ducts, as by its action on the capillary circulation of the glands themselves; for on inhaling the vapour carefully by the nostrils, so that none enters the mouth, I still find that there is an increased secretion of saliva. ”

“ A horse kept on perfectly dry food gives out a far greater quantity than when the food is moistened. Experiments on the dog and rabbit supplied similar results; and, extraordinary as it may appear, the gland will secrete saliva in the course of an hour weighing eight or ten times as much as its own tissue. A striking example this of the rapidity with which saliva can be separated from the blood under certain circumstances, and of the fallacy of founding conclusions on the quantity secreted within the twenty-four hours. ”

“ That gland, which in its sound state secretes pure saliva, may, from being thrown into diseased action, produce a poison of the most destructive quality. Nature appears to have no more difficulty in forming minute glands among the vascular parts of the body than she has in forming blood vessels, and millions of these can be called into existence, when inflammation is excited, in a few hours. ”

“ No statical experiments can ascertain the quantity of our perspiration; as a continued absorption of the moisture of the atmosphere exists at the same time both by the cutaneous and pulmonary lymphatics.
3. Every gland is capable of being excited into greater exertions by an appropriated stimulus applied either by its mixture with the blood immediately to the secerning vessel, or applied externally to its excretory duct. Thus mercury internally promotes an increased salivation, and pyrethrum externally applied to the excretory ducts of the salival glands. ”

“ A part is continued for some distance along the hyo-glossus, crossing the direction of its fibres, and interwoven with them; other fibres seem to bend into the substance of the tongue, near its base and at right angles to its axis. Its surface corresponds to the parotid gland, external carotid artery, internal pterygoid muscle, and mucous membrane of the mouth; deeply, it lies on the internal carotid artery, the superior constrictor of the pharynx, the tonsil and hyo-glossus. ”

“ Permit me, gentlemen, to occupy a few moments of your time in an exposition of this grand operation, and of McClellan's pre-eminent relation to it. The complete extirpation of a diseased parotid gland was considered an impossibility. The under portion of this gland is deeply seated and compacted in among important muscles and bones appertaining to the brain, the organs of hearing, mastication, deglutition and speech. Through its substance pass the external carotid artery and the great nerve of expression and respiration. ”

“ This curtailment of length, indeed, is well seen in the act of swallowing: the larynx is seen to rise upwards to exactly the same degree that the gullet is drawn downwards; while, after the process of swallowing has been completed and the gullet is released from tension, the larynx can be clearly seen to again. This is because the inner coat of the stomach, which has the longitudinal fibres and which also lines the gullet and mouth, extends to the interior of the larynx, and it is thus impossible for it to be drawn down by the stomach without the larynx being involved in the traction. ”

“ And therefore the several Parts of it are separated by their proper Glands, and Nature has planted no fewer than four Pair about the Mouth, which supply the Juices that make the Saliva; to wit, the Parotides, and the Glandulæ Nuckianæ, the {162} Glandulæ Maxillares internæ, and Sublinguales. Whereas if the Saliva were but one more simple Liquor, a less number of Glands might have been sufficient. At least there appears no Reason why one of every Pair should disembogue itself into the Mouth so very near to the Orifice, by which a Gland of some other Pair throws in its Juice ”

“ Because the mucous membrane has become so swollen that the nasal passages are obstructed and the mucous membrane of the larynx has to perform a double function, that of heating the air as it is brought to the lungs in the process of respiration, as well as carrying out its own obligation to the scheme of nature. By a strange coincidence, this membrane of the larynx is supplied with sensation by the same nerve that conveys motion to one of its tensor muscles. ”

“ The spasms rapidly spread to all the muscles of deglutition and respiration, so that the patient not only has the greatest difficulty in swallowing, but has a constant sense of impending suffocation. To add to his distress, a copious secretion of viscid saliva fills his mouth. Any voluntary effort, as well as all forms of external stimuli, only serve to aggravate the spasms which are always induced by the attempt to swallow fluid, or even by the sound of running water. ”