49 6 TEXT-BOOK OF PHYSIOLOGY 



disease the mind becomes dull and clouded, the memory becomes defective, 

 sometimes delusions arise, and frequently dementia supervenes. 



The Effects of Surgical Removal in Man and Animals. The com- 

 plete removal of the thyroid gland by surgical procedures necessitated by 

 grave pathologic conditions has been followed in human beings by a serious 

 morbid condition to which the terms cachexia strumapriva or thyroprivia 

 have been applied. Within a relatively short time the patients complained 

 of muscle fatigue, a sense of heaviness in the limbs and more or less pain. 

 With the progress of the disordered condition there developed a swelling of 

 the face, hands and feet similar to that observed in myxedema. The mental 

 processes became sluggish, the speech difficult and movements slow. A 

 mental condition, approximating idiocy was finally developed before death 

 supervened. With the development of knowledge, regarding the function 

 of the thyroid it was found possible to remove a large portion of the diseased 

 gland without the development of unfortunate results, by leaving behind a 

 small portion, sufficiently large, however, to maintain the necessary amount 

 of internal secretion. 



The extirpation of the thyroid in animals is usually fatal though the 

 effects differ according to the animal operated on. Herbivorous animals 

 as a rule survive the removal of the gland far better than carnivorous animals, 

 though no sufficient reason for this difference has been presented. Dogs 

 usually die in a few weeks, death being preceded by tremors, and convul- 

 sions. Monkeys, according to Horsley's experiments and observations, gen- 

 erally die within a few weeks. 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 termin- 

 ating 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. 



It is evident from the foregoing facts, 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 difference of opinion. 

 The view that the gland removes from the blood certain toxic bodies, render- 

 ing them innocuous and thus preserving the body from a species of auto- 

 intoxication, is gradually yielding to the more probable view that the epi- 

 thelium is engaged in the secretion of a specific material, which finds its 

 way into the blood or lymph and in some unknown way influences 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 Effects of Feeding the Thyroid Gland. On the supposition that 

 the thyroid gland secreted and discharged into the blood an agent necessary 

 to the maintenance of the normal metabolism, it was thought probable that 

 the internal administration of the gland or its extracts might provide the 

 body with the necessary amount of the secretion. Acting on the suggestion, 

 fresh thyroids of various animals, principally from sheep, have been admin- 



