Page:EB1922 - Volume 30.djvu/912

862 Exophthalmic Goitre. This disease is characterized by the three cardinal symptoms, enlargement of the thyroid, protrusion of the eye-balls and a rapid heart beat. It is usually ascribed to an over- secretion of the thyroid gland, though many authors prefer to at- tribute it to a disturbed function of the organ. Complete rest often suffices to cure the condition, though many surgeons recommend removal of a large part of the gland.

Kendall believes that he has isolated the active principle of the thyroid gland, and to this he gives the name of thyroxin. It is al- leged that this substance may be used instead of thyroid substance in cases of thyroid insufficiency and that the results are as satis- factory as when the gland substance is employed.

The Parathyroids. In the great majority of mammals there are four parathyroids, two in relation with each lobe of the thyroid. The glandules do not contain vesicles but consist of solid masses of cells. They are developed from the epithelium of the third and fourth branchial clefts. Most observers do not believe that they are functionally related to the thyroid.

Extirpation of all four parathyroids is rapidly fatal in the case of many animals. Where death does not occur it is usually as- sumed that accessory parathyroids are present. It is certainly true that in many of the herbivora such accessory glandules are frequently present. The symptoms which occur after extirpation are those of tetany muscular spasms, rapid respiration, saliva- tion, etc. The condition is now usually called tetania para- thyreopriva, and Koch and Noel Paton ascribe it to intoxication by guanidin. They believe that the parathyroids control the metabolism of guanidin and in this way exercise a regulative action upon the tone of the skeletal muscles.

Idiopathic Tetany. Since the symptoms of this disease strikingly resemble those of tetania parathyreopriva, it is now very generally believed that they are due to disease of the parathyroid. It is sometimes alleged also that paralysis agitans, chorea, epilepsy, and eclampsia are due to disturbance of the functions of these bodies.

The Pituitary Body. The pituitary body consists of two principal portions, the anterior or glandular, and the posterior or nervous. The former is developed as an evagination from the ectoderm in the buccal region. The posterior portion is an outgrowth from the base of the brain. Covering the latter is a second glandular portion called the pars intermedia.

The glandular portion seems to give rise to substances which are essential for the proper development of the skeleton and other tissues of the growing animal, and Robertson states that he has succeeded in isolating from this lobe a substance called tethelin, which hastens growth in young animals. Pituitary feeding is stated to increase the output of eggs in laying hens.

Extirpation experiments seem to point to the anterior lobe as the part which is essential to life. But from the posterior lobe certain active extracts can be obtained. These extracts when injected into the circulation of a living animal produce a rise of blood pressure which is more prolonged than that produced by adrenin, but a second injection may produce a fall. The extract produces a sthenic effect upon uterine contractions and upon those of the intestine and bladder. It also causes dilatation of the pupil and constriction of the bronchioles. Pituitrin also causes a marked increase in the flow from the kidney and the mammary gland. A striking effect on metabolism produced by the administration of pituitary substance is a lowering in the tolerance for sugar.

DISEASES OF THE PITUITARY. Hyperpituitarism. Overgrowth of the anterior lobe usually of an adenomatous nature gives rise to increased growth of the bones of the extremities and of the face, and, if it occurs in young subjects, to gigantism, when, as in older sub- jects, it chiefly affects the face and the ends of the long bones, the condition is called acromegaly. Diminished sugar tolerance usually' supervenes as the other parts of the organ become affected. There may be actual glycosuria and frequently polyuria.

Hypopituitarism. In this condition the body does not grow, although there may be an extensive deposition of fat. There is marked failure in sexual development. Sugar tolerance is very pro- nounced and there is arrested mental development. In cases which do not arise until adult age has been reached obesity and increased sugar tolerance are the most striking symptoms.

A functional relationship between the pituitary and the other ductless glands (especially the thyroid) is more than probable.

The Pineal Gland This tiny structure has usually been considered as belonging to the group of " vestigial remains," and its chief interest to morphologists centres round its homology with the median eye of reptiles. It is developed as an outgrowth from the third ventricle of the brain. But even in lower vertebrates there is some evidence that a glandular constituent has to be reckoned with. Within the last few years numerous writers have urged that in mammals, including man, the organ is of considerable importance, and that it belongs to the group of glands furnishing an internal secretion.

Extirpation experiments have been carried out in some ani- mals, and it is stated that removal of the organ accelerates growth of the body and especially of the reproductive apparatus, or at any rate a hastening of the development of the reproductive functions.

Tumors of the pineal gland are associated with abnormal growth of the skeleton in children, and with early and precocious develop- ment of the secondary sexual characters. In order to correlate these findings with the results of extirpation experiments it is assumed that the tumour gives rise to a condition of hypopinealism. It will be remembered that the common tumours of the pituitary body are considered to be adenomata and to give rise to a hypersecretion.

Injection of extracts made from the pineal gland give rise to no special effects upon the blood pressure, respiration, secretion of glands, or other functions which can be investigated by ordinary kymographic methods. But it is alleged that administration of extracts over a long period to growing animals hastens the growth and development of the reproductive organs. If these statements are correct they only tend in the present stage to complicate the problem, for it is certainly contrary to expectation to learn that removal of an organ from an animal and its administration to the animal as food or drug will produce similar results. The whole sub- ject is obscure, and here, as in the case of some other of the ductless glands, it is probable that our experimental technique is too faulty or too limited to enable us yet to draw any just conclusions.

The Testes. The effects of castration in man have been known for a very long time. The absence of hair from the face, the undeveloped larynx and the persistent soprano voice result- ing, and the tendency to gigantism and obesity are among the more striking of the characters of a eunuch. In male stags the antlers do not grow, and in the cock the comb fails to develop. These results do not occur when the vas is tied. In some animals and under favourable conditions these secondary sexual characters may be induced if a testis is transplanted from another animal. So that they must be attributed to an absence of a specific internal secretion.

The elements of the testis which are usually supposed to furnish the internal secretion are the interstitial cells of Leydig. These are of an epithelioid character and contain lipoid granules. These structures are not always very striking in sections through the testis, but they are more marked in some animals than in others.

Injection of extracts of the testis was observed many years ago by Brown-Sequard to have a rejuvenating or stimulating effect upon the subject so treated, but it is doubtful whether the effect is specific or more marked than with other extracts.

The Ovaries. It is well known that if both ovaries are removed from a young animal the uterus does not develop, menstru- ation does not occur, and the mammary glands fail to grow.

Extracts made from the ovary produce certain effects upon smooth muscle, but it is not certain that these effects are specific.

The corpus luteum appears to be concerned with the fixation of the embryo in utero and also with the growth of the mammary gland and the secretion of milk. As in the case of the testis there is a tendency to attribute the internal secretions of the ovary to cer- tain interstitial cells. These, however, are not present in all animals or at any rate are not present during all periods of the sexual cycle.

Extracts of ovary have been employed in the same manner as those of testis, and the same criticism applies.

The Carotid Body. Situated at the bifurcation of the carotid artery and consisting, in many animals, of only a few cells, it is not known that the carotid body, or carotid gland, carries out any important functions. Among the constituent cells are a few of the chromaphil variety, and these are capable, presumably, of furnishing a small amount of adrenin to the general circulation.

The Coccygeal Body. This structure is included in our list because it has been alleged that it contains chromaphil cells. This, however, does not appear to be the case. The body is apparently an arterio-venous anastomosis. (S. V.) DU MAURIER, GERALD (1873- ), English actor, was born at Hampstead March 26 1873, the son of George Du Mau-