On the comparative anatomy of the thyroid gland / [John Simon].

  • John Simon
Date:
1844
Catalogue details

Licence: Public Domain Mark

Credit: On the comparative anatomy of the thyroid gland / [John Simon]. Source: Wellcome Collection.

    4/12 page 296
    They were first, I believe, mentioned by Perrault* and were afterwards described in several genera of Birds by Ballanti^ and Uttini. Various later observers have since noticed these bodies ; some considering them as thyroid glands ; while others, among whom are Meckel, Cuvier and Haugsted, entertain a different opinion of their nature. In all such uncertainties the microscope is the only conclusive test. By repeated and careful examinations, I have satisfied myself that the ultimate structure of these doubtful organs is identical with that of the thyroid gland in Mammalia. They con¬ sist, namely, of a dense aggregation of closed vesicles, whereof each is constituted by a delicate homogeneous membrane, is invested by a close capillary net-work, and contains in its interior either floating cytoblasts, or mature cells, corresponding to those of the true glands. My dissections of Birds have included all the orders, and, in most instances, several families from each : I have never failed to find the thyroid gland, or to recognise its peculiar structure : I accordingly presume that it is universally present in this class of animals. Of its relative position it is unnecessary to say much more than is included in the notices of previous observers, and I will merely mention that its relation to the larynx seems neither essential nor constant. A more uniform and more important relation is included in the fact, that the gland always corresponds to a particular spot of the vascular system ; namely, that it lies on the cervical vessels, and receives its supply of blood just opposite to the point at which the vertebral and carotid arteries diverge to their respective destinations. \ II. Reptiles. It is unaccountable that in this class of animals, where the thyroid gland is univer¬ sally manifest, it should have been so generally overlooked. Where noticed, it has been, with rare and partial exceptions, either mistaken for the thymus, or confounded with it in a common description. A. Chelonia. Bojanus, in his excellent monograph on the freshwater Tortoise^, figures with perfect fidelity the body, which I shall directly mention as the thyroid gland ; but he does so under the erroneous impression that it is a thymus, and describes it by this name: Carus^ likewise falls into the same error as to its true nature. * Description de six Otardes, Mdm. de l’Acad. t. iii. part 2. p. 319. t Ballanti states an opinion of their use which has received pretty general sanction :—“ quod vocis organo famuletur glandula hujusmodi in animantibus, id videtur satis comprobare ejus sedes, quae nunquam non est cum eo organo conjunctaand Uttini, who continued his researches, specifies this function more exactly, as being “ ad vocales chordas opportune emolliendas et humectandas.” Comment. Bonon. 1783 ; De Organo Vocis. + Anat. testudinis Europ. figs. 66, 156, 173. § Op. cit. § 740.
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