Till THYROID \M» PARATHYROID GLAN 753 



looked thai the effects produced by thyroidectomy and parathyroid- 

 ectomy are often verj differenl in animals of the same kind at dif- 

 fered ages. Speaking generally, i1 may be said thai the influence of the 

 parathyroid is focused mainly on the nerve centers and only to a second- 

 ary degree on the metabolic functions, whereas the reverse is th< 

 with the thyroid, its main effecl being on metabolism, although it prob- 

 ably also exercises a secondary effecl on the aerve centers. Mori 

 than in the case of any other endocrine organ, our knowledge concerning 

 the function of the thyroid has been gained by clinical experience, -• i n < 1 



it is difficull to saj whether the clinical or the experimental t h « ►< 1 has 



contributed the greater amounl of information. 



The results of experimental extirpation of the thyroid vary accord- 

 ing to the age of the animal, and frequently they are by no means 

 marked, provided sufficienl parathyroid tissue has been undamaged. 

 The symptoms are in general thickening and drying of the skin, with ;i 

 tendency to adiposity and a loss of i • of the muscle. The body tem- 

 perature is low and the sexual functions I me subnormal. Nervous 



symptoms in the direction of mental dullness and lethargy are also 

 usually present. Surgical removal of the thyroid in man produces the 

 condition known as cachexia strumipriva. The symptoms may first of 

 all become a]. parent a few days after the operation, or they may remain 

 latent for years, and then develop so as to produce the condition known 

 as myxedema. When nervous symptoms are prominent in cachexia 

 strumipriva, it is usually taken as evidence that an excessive amount 



of parathyroid tissue has hen destroyed. ECocher states that after com- 

 plete h>ss of the thyroid, life is impossible for more than seven years, 

 and thai to prevent ultimate ill effects, at leasl one-fourth of the organ 



should be left intact. 



Disease of the Thyroid 



The symptoms of diseased conditions of the thyroid may be inter- 

 preted as the consequence of increased or diminished Functioning of the 

 gland. Sometimes, however, the less active gland is really inc 1 in 



hulk, this increase being caused by the accumulation in it of very large 

 quantities of colloid material accompanied by an attenuated condition 

 of the vesicular cells (see page 751 . When the gland is atrophied at 

 birth, the condition of cretin on becomes developed Fig. 194 . The 



Characteristic features of cretinism are: 1 An arr. gTOWtl 



cially of the skeleton, accompanied by incomplete ossification of the long 



hones and failure of the fontanelles of the skull I •• properly. 



Poor development of the muscular system. :: An unhealthy, dry. swollen 

 condition of the skin, s.. that it is yellowish in color, the face being pale 



