SUPRARENAL CAPSULES 43 



It has been much debated whether the thyroids form an 

 internal secretion which is necessary to the organism or whether 

 they destroy toxic substances formed elsewhere in the body. 

 In favor of the latter view is the fact that after thyroidectomy 

 the organism cannot cope so readily with poisons introduced 

 from without. There is no evidence that an actual destruc- 

 tion of toxic substances takes place in the gland itself. A 

 far more probable view of the thyroid function is that its 

 secretion is indispensable to the maintenance of the normal 

 level of nutrition, especially of the central nervous system. 



It is likely that the secretion of the thyroid is under the 

 influence of nerves, for section of the superior and inferior 

 thyroid nerves is followed by degenerative changes in the 

 gland. 



Parathyroids. Parathyroidectomy after a series of acute 

 symptoms ends fatally within ten days. The symptoms are 

 those of tetany. Tremors, increasing in severity, end in spas- 

 modic attacks and in general convulsions. The pulse rate 

 and respirations are markedly increased; profuse salivation 

 and fever exist. The administration of calcium completely 

 relieves these symptoms and in some animals death may, 

 perhaps, be indefinitely postponed. The tetany produced 

 by ammonia compounds is precisely like that of para thyroidec- 

 tomy, and it has been shown that the percentage of ammonia 

 in the blood is the same in both cases. 



Suprarenal Capsules. The extirpation of the adrenals in 

 animals leads to a rapid death. Their disease in man, known 

 as Addison's disease, manifests itself in loss of vascular tone, 

 anemia, muscular weakness, and bronzing of the skin. Experi- 

 mentally it has been shown that intravenous injection of 

 extracts into animals brings about a rapid rise of blood pressure, 

 owing to a constriction of the arterioles and to a strengthening 

 of the heart beat. The heart beats more slowly, however, 

 on account of a reflex inhibition through the vagi. If these 

 are cut the blood pressure rises to enormous heights, possibly 

 to four or five times the original height. There is reason to 

 believe that the active principle of such extracts, adrenalin, 

 also affects the vasomotor centre. It is said to exert its action 

 mainly on structures supplied by sympathetic nerve fibers. 

 The effect is still more pronounced when the nerve fibers have 



