196 THE DUCTLESS GLANDS. INTERNAL SECRETIONS. 



gelatin, albumin, sodium albuminate, sugar and fat leucin, thymus-nucleinic acid r 

 xanthin, hypoxanthin; formic, acetic, butyric, lactic, and succinic acids. In the 

 ash, potassium and phosphoric acid preponderate over sodium, calcium, magnesium 

 (ammonium ?) , chlorin, and sulphuric acid. 



Extirpation of the thymus gland in the frog is fatal. According to Svehla the 

 infusion of thymus juice causes a fall of blood-pressure and acceleration of pulse, 

 while large doses are fatal. 



The thyroid gland is an organ provided with vasomotor and secretomotor 

 nerves, and composed of a richly cellular connective-tissue framework, containing 

 closed circular or oval acini (from 0.04 to o.i mm. in diameter), which in the 

 embryo and the new-born are lined with a single layer of nucleated, granular, 

 cuboidal cells. In 50 per cent, of all subjects accessory thyroid glands, up to 

 four, are associated with the main gland; a small detached gland is occasionally 

 found in front of the descending aorta. In addition, accumulations of epithelial 

 cells are found in the acini and, in embryos, also beneath the common capsule. 

 From birth the cells secrete a colloid substance by a transformation of their proto- 

 plasm, at the same time undergoing morphological changes. Some of the cells 

 are destroyed in this process of colloid degeneration. 



The acini of the thyroid gland evacuate their contents in part by rupture, 

 with destruction of the epithelium, in part, in the process of pure colloid-produc- 

 tion, by secretion into the intercellular interstices; and in this way the secretion 

 reaches the interfollicular lymph-spaces and then the blood. 



Blood-vessels of considerable size and importance enter the organ. Lymph- 

 vessels partly begin in the interior among the acini, and partly form a network in 

 the capsule that surrounds the entire organ. 



The constituents of the thyroid gland are colloid, nucleoalbumin, iodothyrin, 

 leucin, xanthin; lactic, succinic, and volatile fatty acids. 



According to Schiff, Zesas, J. Wagner and others, extirpation of the thyroid 

 gland is followed by death, with the symptoms of chronic intoxication. Dysphagia, 

 vomiting and digestive disturbances, acceleration of the breathing; later dyspnea, 

 alteration of the action of the heart, somnolence, slow and hesitating movements 

 with fibrillar twitchings, which may go on to intermittent tonic convulsions (tetany) , 

 palsies, alterations in cutaneous sensibility, desquamation of the skin, lowering of 

 the body-temperature and of the blood-pressure, are the symptoms that precede 

 death. Albuminuria, reduction of the amount of oxygen in the arterial blood 

 and degenerations in the central and peripheral nervous system were observed by 

 Albertoni and Tizzoni, Langhans, Kopp and Capobianco. In man, also, total 

 extirpation of the thyroid gland (cachexia strumipriva) is a serious matter and 

 often terminates fatally from tetany. 



The morbid phenomena may be counteracted, at least temporarily, by the 

 internal administration of fresh or dry thyroid-gland substance, or by the sub- 

 cutaneous injection of thyroid-gland extract or iodothyrin. The symptoms may 

 be prevented by grafting a thyroid gland successfully in some other portion of 

 the body, and permitting the organ to form adhesions. These facts prove that 

 the thyroid gland produces a substance that is indispensable for normal metabo- 

 lism. Stated more accurately, the function of the thyroid gland is to neutralize 

 a substance produced in the body, the accumulation of which has a toxic influence 

 on the nervous system. 



The accessory thyroid glands and the hypophysis appear to possess similar 

 functions: they undergo compensatory hypertrophy after extirpation of the thy- 

 roid gland. Other investigators attribute the condition known as myxedema, 

 that is, mucoid infiltration of the subcutaneous tissues of the head and neck, with 

 profound disturbances of the nervous system, to the point of idiocy, to loss of the 

 function of the thyroid. 



Especially noteworthy is the enlargement of the thyroid gland, together with 

 the palpitation of the heart and protrusion of the eyeballs, in the condition known 

 as exophthalmic goiter, which appears to be due to simultaneous (toxic ?) irritation 

 of the accelerator nerve of the heart, the sympathetic fibers of the unstriated 

 muscles in the orbit and in the eyelids, as well as of the dilator nerves of the 

 vessels of the thyroid gland. Myxedema and exophthalmic goiter seem to stand 

 in a certain antagonistic relation to each other, the former depending on diminished, 

 the latter on augmented, activity of the thyroid gland (hence extirpation has been 

 recommended in cases of exophthalmic goiter). Landois observed in dogs that 

 had been fed on thyroid glands a marked increase in the number and force of the 

 cardiac contractions. The ingestion of thyroid gland causes an increased con- 



