386 NELSON W. JANNEY 



and Surgery. Mechanical injury to the neck is a very rare 

 cause of myxedema as, if but a small portion of the gland remain intact, 

 it can usually replace the whole as to function. 



Surgical removal of the entire thyroid was formerly an important 

 cause of myxedema (cachexia strumipriva) , and led to the recognition of 

 the etiological connection of the thyroid with myxedema (Kocher, Eever- 

 din). Experimental thyroidectomy in animals has clearly shown the 

 necessary presence of the thyroid to prevent hypothyroidism in its severest 

 manifestations (Grley, Vassale and Generale, Pineles, Erdheim, Chvostek). 

 A large variety of animals are now known to develop cretinic characteris- 

 tics after thyroidectomy. Typical instances of cachexia strumipriva -in 

 human beings are quite rare at present, since it is recognized that the 

 retinition of a certain amount of thyroid tissue is necessary for normal 

 thyroid function. Occasionally, however, the remaining portion of the 

 gland atrophies with resulting complete myxedema. More often only mild 

 hypothyroidism develops if overmuch of the gland has been removed. 

 Certain old operated cases exhibit a unique mixture of thyrotoxic and 

 thyroprivic symptoms and are to be classed under the category of 

 dysthyroidism. 



The complete surgical removal of the thyroid in children is followed 

 by cretinism without exception. Most writers quote the classical case, 

 then a child of ten years, from whom the thyroid w r as extirpated by Sick 

 in 1867. When observed by Bruns eighteen years later, typical cretinism 

 had developed. Similar disastrous results of complete thyroidectomy in 

 childhood were reported by Kocher, Combe, et al. 



Pathology 



The lesions met with in hypothyroidism are local, i. e., in the thyroid 

 gland itself, and general, affecting all organs and tissues. Pathological 

 changes in the thyroid gland invariably accompany hypothyroidism. To 

 quote Th. Kocher, that great student of thyroid disease, "Without lesions 

 or absence of the thyroid no myxedema." Congenital absence of the thy- 

 roid, tliyr^aplama, will first be considered in the text, then the changes in 

 the gland met with in hypothyroidism, followed by a systematic descrip- 

 tion of organic pathology due to the lack of the thyroid secretion. 



Thyroaplasia. It was not until the beginning of the 20th century 

 that the possibility of .congenital absence of the thyroid gland was sug- 

 gested by Siegert upon clinical data and demonstrated pathologically by 

 Pineles. It was later recognized that the thyroid may be hypoplastic at 

 birth, never attaining normal size and function, also that very rarely one 

 lateral lobe may be missing (see further studies by Erdheim (&) and Diet- 

 t'l'le (fo)). Pineles described twelve cases of supposed thyroaplasia based 



