In Bright's disease two to six thyroid glands of the sheep per week increase the density of the urine and the quantity of urea is augmented very sensibly. Gif ford (Brit. Med. Jour., Mar. 31, '94).
Study of sixty cases. The action of thyroid extract is complex. It undoubt edly produces a mild, feverish condition, the action and reaction of which are often of considerable benefit. It is a direct cerebral stimulant. There is a strong probability that at some periods of life the administration of the thyroid supplies some substance necessary to the bodily economy. Bruce (Jour. of Mental Science, Oct., '94).
Experiments on dogs showing that after removal of the thyroid the urotoxic coefficient rose to nearly double. The toxicity of the blood-serum also increased after thyroidectomy. The thyro-iodine of Baumann, when given to athyroidized dogs, caused the urotoxic coefficient to return almost to the normal, and re lieved most of the nervous symptoms. Spoto ((lion dell Assoc. di Napoli, p. 526, '96).
Five mice and three guinea-pigs were treated with thyroid extract. Swelling of the face, emaciation, and loss of strength. In all cases the administra tion was continued till the animal died. No lesion found of either nerve-elements or neuroglia; no varicose or atrophied dendrites or loss of gemmulm. The cor pora showed no loss of angularity, and the axons and appendages were all healthy. No nuclear change in the cells ascertained; the blood-vessels were care fully examined without the discovery of any lesion. It would seem from these investigations, so far as they go, that the toxic action of thyroid is of a different nature from that of other conditions, and one which we are not, therefore, in a position to understand. Berkley (Bulle tin of the Johns Hopkins Hospital, July, '97).
Two main hypotheses have been ad vanced as to how the secretion of the thyroid acts on the tissue of the body: First, that the tissue forms toxic sub stances which are neutralized by the thy roid secretion: this is the antitoxic theory. Second, that the thyroid secre tion promotes or regulates normal metab olism; this is the trophic hypothesis.
All the newer evidence seems to point to the latter as the more probable one. H. Sneve (Columbus Med. Jour., Dec. 20, '98).
The thyroid gland is not to be re garded as an organ pouring a useful in ternal secretion into the circulation; the lymph leaving it, and the lymphatic glands in the vicinity, do not contain iodine; and the blood and central nerv ous system in healthy animals are also free from iodine. Removal of the thyroid is followed by disease and death, because the organ which removes poisonous sub stances from the blood can no longer pro tect the animal. It is the central nervous system which principally suffers, and by Nissl's method great changes (chroma tolysis) can be demonstrated in the ganglion-cells. The thyroid, therefore, appears to be the great protective organ to the central nervous system. The poisonous substances are destroyed by oxidation, and this appears to be assisted by combinations with the iodine. F. Blum (Pflueger's Archly, 70, .99).
Iodine-holding proteid compounds are almost wholly separable from the gland by water. The total iodine of the gland is so distributed that about 90 per cent. can be separated by alcohol. acids, etc., as iodo-albumin compounds in firmly bound form. Thyroidin does not occur free in the gland. R. Tamhach (Zeit. f. Biol., xxxvi, No. 4. p. 549, '99).
Removal of the thyroid alone invari ably causes myxcedema, while removal of the four parathyroids produces the acute tetanic symptoms observed after so-called experimental "thyroidectomy." The partial tetany sometimes observed after apparent removal of the thyroid in man is most likely really due to the inadvertent removal of some of the parathyroids along with the thyroid proper. The symptoms of myxcedema can be fully explained by the absence of iodotbyrin from the blood which such removal entails, and the symptoms of parathyroideetomy are not yet sus ceptible of any satisfactory explana tion. Robert Hutchison (Practitioner Apr., 1901).