. The biology of the frog. Frogs. xii INTERNAL SECRETION AND DUCTLESS GLANDS 223 thyrin, thyroiodin). Little is known of its function in the frog. In the higher vertebrates its removal is followed in nearly all cases by fatal effects. Removal of only a part of the gland, as a rule, creates but little disturbance. Life may be maintained for a considerable period after complete removal of the thyroid, by giving injections of extracts of the gland into the blood. In man the disease called myxoedema or cretinism, caused by the atrophy of the thyroid, is often much helped or even cured by the
. The biology of the frog. Frogs. xii INTERNAL SECRETION AND DUCTLESS GLANDS 223 thyrin, thyroiodin). Little is known of its function in the frog. In the higher vertebrates its removal is followed in nearly all cases by fatal effects. Removal of only a part of the gland, as a rule, creates but little disturbance. Life may be maintained for a considerable period after complete removal of the thyroid, by giving injections of extracts of the gland into the blood. In man the disease called myxoedema or cretinism, caused by the atrophy of the thyroid, is often much helped or even cured by the administration of thyroid extract. The substance to which the thy- roid owes its important function is a proteid with which a compara- tively large amount of iodin is in combination. Treupel found that frogs from which both thyroids were removed lived only two or three days, but he was not entirely certain that the result might not be due to effects of the operation other than the loss of the parts in question. The Thymus. - The thymus is a small, oval organ, some- what reddish in color, situated behind the tympanic mem- brane under the depressor mandibulae muscle. As in most higher forms, the thymus diminishes in size with age. Maurer found that in Rana esculenta the thymus attained its maxi- mum size in specimens of two or three centimeters in length. In old frogs (7 to 8 cm.) the organ is much smaller and shows marks of degeneration in structure. The thymus has essentially the structure of a lymphoid gland. In its fine network of adenoid tissue lie numerous small, rounded cells. There are also several large cells of concentric structure concerning whose origin and significance FlG. 62. — Diagram showing the position of the thymus, 'Ik. Dm, depressor mandibulae muscle; 7y, Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly r
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Keywords: ., bookauthorholmessamueljsamuelja, bookcentury1900, bookdecade1910
