HYPOTHYKOIDISM 389 



effects of loss of the normal function of this vital hormone producing 

 center. (1) Characteristic of the changes in the young and growing 

 organism are retardation and cessation of growth. We therefore observe 

 tissues and organs in a state of development far earlier than -the real age 

 of the hypothyroid individual. (2) In addition is found at times a new 

 pathological tissue peculiar to the disease, which may pervade the skin 

 as well as deeper parts. (3) There is also to be considered the effects 

 of bacterial and other toxins upon an organism deprived of its usual 

 powers of defence, i. e., its normal supply of the thyroid hormone which 

 is essential to maintain the normal resistance against bacterial invasion. 



Unfortunately, the pathological researches on hypothyroidism have 

 been chiefly directed, as so often- in medicine, at the most striking anom- 

 alies, the thyroid itself, the myxedematous tissue, and the skeleton. Few 

 researches have been made on other important organ systems so that our 

 knowledge of their condition in the subthyroid state still remains de- 

 fective. Many pathological changes such as those of the cutaneous ap- 

 pendages are of symptomological interest and importance. In order, 

 therefore, to avoid later repetition, the present pathological description is 

 chiefly confined to a notation on myxedema and the deep-seated lesions 

 due to defective thyroid function. 



Myxedema. This peculiar substance is found in greatest quantities 

 in the subcutaneous and submucous areas. It may, however, infiltrate 

 various organs and tissues, brain, liver, kidney, muscle, etc. The amount 

 is subject to great variation and may even disappear late in the disease. 

 By the older observers of hypothyroidism, it was regarded as mucin 

 (Ord, Horsley, Halliburton) . On closer study, however, it has come rather 

 to be regarded as more complex material. Histologically the connective 

 tissue of the chorion resembles granulation tissue, is markedly hyper- 

 trophied, gelatinous and contains increased numbers of nuclei and fibrils. 

 The lymph spaces are distended with a mucoid material which has not 

 been subjected to a thorough modern chemical study. Virchow consid- 

 ered with insufficient reason these changes irritative, resembling granula- 

 tion tissue. The best supported view, however, regards myxedema as 

 a reversion to an embryonic type of tissue such as is found in the umbilical 

 cord. Little new data have been added in recent years to our knowledge 

 of this peculiar pathological product, which urgently requires restudy 

 with the aid of modern chemical technique. 



Nervous System. The central nervous system suffers severely. The 

 brain in thyroaplasia may show defective convolution and all parts of 

 the central, peripheral and autonomic nervous systems exhibit the signs 

 of retarded and deficient development. This condition is accompanied 

 by degenerative changes which, according to Edmund's (c) experiments in 

 animals and Mott's cli'nical observations, consist in a general chrom- 

 atolysis, especially marked in the vagal and glossopharyngeal nuclei. 



