THE PITUITA RY BODY. 945 
That the thyroid gland yields an internal secretion which subserves a 
useful purpose within the body, appeals 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 flow, 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 tum- 
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 myxcedema, 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 w T e 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 mcd. JFchnsch,:. Leipzig, 1887, S. 227 (quoted bv Waldeyer). 
3 Berl. Min. JFchnschr., 1887, S. 233. 
4 Centralbl.f. Physiol., Leipzig u. Wien, 1S97, 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 Compl. rend. Soc. de biol., Paris, 1892, p. 509. 
7 Arch. ital. de biol., Turin, 1895, tome xxii. p. 133. 
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