144 HUMAN PHYSIOLOGY. 



Extirpation of the thyroid, for relief from symptoms 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 experiments on 

 dogs, and found again that removal of the thyroid was speedily followed by 

 tremors, convulsions, and death. Similar experiments were made by Hors- 

 ley on monkeys, with results which resembled those characteristic of myx- 

 edema. 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; 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 symp- 

 toms observed in monkeys was divided by Horsley into three stages: viz., 

 the neurotic, the mucinoid, and the atrophic. It is evident that the presence 

 of the thyroid is essential to the normal activity of the tissues generally. As 

 to the manner in which it exerts its favorable influence, there is some differ 

 ence of opinion. The view that the gland removes from the blood certain 

 toxic bodies, rendering them innocuous, and thus preserving the body from 

 a species of auto-intoxication, is gradually yielding to the more probable 

 view that the epithelium is engaged in the secretion of a specific material, 

 which finds its way into the blood or lymph and in some unknown way in- 

 fluences favorably tissue metabolism. This view of the function of the 

 thyroid is supported by the fact that successful grafting of a portion of the 

 thyroid beneath the skin or in the abdominal cavity will prevent the usual 

 symptoms which follow thyroidectomy. The same result is obtained by 

 the intravenous injection of thyroid juice or by the administration of the 

 raw gland. It was shown by Murray that myxedematous patients could be 

 benefited, and even cured, by feeding them with fresh thyroids or even with 

 the dry extract. 



The chemic features of ' the material secreted and obtained from the 

 structures of the thyroid indicate that it is a complex protein containing 

 iodin, which, under the influence of various reagents, undergoes cleavage, 

 giving rise to a non-protein residue, which carries with it the iodin and 

 phosphorus. The amount of iodin in the thyroid varies from 0.33 to i 

 milligram for each gram of tissue. To this compound the term thyroiodin 

 has been given. The administration of this compound produces effects 

 similar to those which follow the therapeutic administration of the fresh 



