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TEXT-BOOK OF PHYSIOLOGY. 



being as well as in animals. The results, however, which follow its extirpation 

 are not always uniform in all animals, though sufficient reasons for the 

 lack of uniformity cannot always be assigned. 



Cretinism, a condition characterized by a want of physical and mental 

 development, is associated with, if not directly dependent on, a congenital 

 absence of the thyroid, or its arrested development during the early years 

 of childhood. 



Myxedema, a condition of the skin in which there is a hyperplasia of 

 the connective tissue, of an embryonic type, rich in mucin, is generally 



regarded as one of the 

 effects of degenerative pro- 

 cesses in the thyroid in the 

 adult. Partly in conse- 

 quence of this change in 

 the skin the face becomes 

 broader, swollen, and flat- 

 tened, giving rise to a loss 

 of expression. At the same 

 time the mind becomes 

 dull, clouded, even approxi- 

 mating the idiotic type. 

 This supposed infiltration 

 of the skin with mucin was 

 termed myxedema by Ord, 

 who at the same time asso- 

 ciated it with a change in 

 the structure of the thyroid 

 as a result of which it be- 

 came functionally useless. 



Extirpation of the thy- 

 roid, for relief from symp- 

 toms due to grave patho- 

 logic changes, has been followed in human beings by symptoms similar to 

 those of myxedema. To this condition the terms operative myxedema and 

 cachexia, strumipriva have been applied. 



After the publication of the history of the myxedema which followed 

 surgical removal of the thyroid, Schiff, in 1887, repeated his earlier experi- 

 ments on dogs, and found again that removal of the thyroid was speedily 

 followed by tremors, convulsions, and death. Similar experiments were 

 made by Horsley on monkeys, with results which resembled those character- 

 istic of myxedema. Among the symptoms which developed within a few 

 days after the removal of the gland may be mentioned loss of appetite; 

 fibrillar contractions of muscles; tremors and spasms; mucinoid degeneration 

 of the skin, giving rise to puffiness of the eyelids and face and to a swollen 

 condition of the abdomen; hebetude of mind, frequently terminating in 

 idiocy; fall of blood-pressure; dyspnea; albuminuria; atrophy of the tissues, 

 followed by death of the animal in the course of from five to eight weeks. 

 The complexus of symptoms observed in monkeys was divided by Horsley 

 into three stages: viz., the neurotic, the mucinoid, and the atrophic. 



FIG 211. A LOBULE FROM A THIN SECTION OF THE 

 THYROID GLAND OF AN ADULT MAN. i. Colloid sub- 

 stance. 2. Epithelium. 3. Tangential section of a tubule, 

 the epithelium viewed from the surface. 4. Tubule in 

 transverse section. 5. Connective tissue. (Stohr.) 



