THE PITUITARY BOD Y. 945 



That the thyroid gland yields an internal secretion which subserves a 

 useful purpose within the body, appears to follow conclusively from these 

 data, and the effects which follow thyroidectomy are probably due to 

 the loss of that secretion. Whether the gland also possesses the 

 function of destroying toxic products of metabolism which would other- 

 wise tend to accumulate in the blood, a function which has been 

 attributed to it by some authors, is a point the evidence regarding 

 which is at present insufficient. 



On account of its extreme vascularity and its direct connection with 

 the vessels which supply blood to the head, the thyroid has also been 

 regarded as exercising a regulatory function on the blood supply to the 

 brain, short-circuiting by vaso-dilatation the cerebral blood How, or vice 

 versd. This view, which was long previously enunciated by J. Simon, 1 

 has been of late again brought into prominence by Stahel, 2 whose 

 opinion is supported by that of Waldeyer, 3 both of whom approach 

 the subject from the anatomical standpoint. More recently the matter 

 has been the subject of physiological experimentation by Cyon, 4 who 

 finds that the nerves passing to the thyroid contain powerful vaso- 

 dilatators, and that their stimulation may greatly lower the pressure in 

 the carotid. Cyon further states that they are called into action 

 very easily on excitation of the cut ends of the vagi, of the depressors, 

 or of the cardiac branches of the recurrent laryngeal nerves. After 

 removal of the gland, the excitability of these nerves is diminished, but 

 it is increased by the administration of thyroid preparations. 



The mode of connection which unquestionably exists between turg- 

 escence of the thyroid and the other nervous and vascular symptoms 

 which characterise Graves's disease (exophthalmic goitre), is still quite 

 obscure. This affection is not, like ordinary goitre and myxoedema, bene- 

 fited by thyroid feeding ; but various observers have obtained consider- 

 able benefit by administration of the uncooked thymus of young animals. 5 



THE PITUITARY BODY. 



The next organ the internal secretion of which we may shortly con- 

 sider, is the pituitary body. As is well known, the anterior lobe of 

 the pituitary body is a structure which may in general terms be described 

 as glandular, and although not in all respects resembling the thyroid, 

 there are nevertheless certain points both in connection with its mode 

 of development, and in the structure of the fully formed organ, which 

 might lead to the supposition that there is something functionally 

 common to the two organs. 



Effects of removal and disease. So far as destruction of the 

 pituitary body is concerned, experiments have given interesting results. 

 The organ has been removed successfully in a number of cases in cats by 

 Marinesco, 6 and in dogs by Vassale and Sacchi. 7 In all instances of 

 complete removal death ensued, usually within a fortnight of the 



1 Phil. Trans., London, 1844, p. 295. 



- Deutsche med. Wchnschr., Leipzig, 1887, S. 227 (quoted by Waldeyer). 



3 fieri. Uin. Wchnschr., 1887, S. 233. 



4 CentralU.f. PhysioL, Leipzig u. Wien, 1897, S. 357. 



5 For the literature of this disease, see Ord and H. Mackenzie, in Allbutt's "System of 

 Medicine," 1897, vol. iv. p. 508. 



6 Compt. rend. Soc. de Uol., Paris, 1892, p. 509. 



7 Arch. ital. de Uol., Turin, 1895, tome xxii. p. 133. 



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