386 EXAMPLES OF CHEMICAL CORRELATION 



administration of thyroid tissue, so far from enhancing the tolerance 

 for acetonitrile, actually renders the animals more sensitive than usual 

 to intoxication by this poison. 



Hyperthyroidism occurs spontaneously in the condition known as 

 Basedow's Disease, or Exophthalmic Goiter. This condition is accom- 

 panied by enlargement of the gland and a marked increase of secreting 

 cellular elements, the interspaces filled with colloidal material which 

 are characteristic of the structure of this gland being much reduced 

 in size. There is a greatly enhanced metabolism, the calorific output 

 being frequently twice the normal; there is a slow progressive loss of 

 weight, incoordination o the heart-beat (Tachycardia), the tempera- 

 ture is supernormal, the nervous system hyperirritable, and the blood- 

 pressure is usually abnormally high. The rate and intensity of living 

 is in fact increased in all its aspects, and frequently to a dangerous 

 extent. The administration of thyroid preparations, or in fact of any 

 iodine-containing substance, leads to a reduction of the Hyperplasia 

 of the epithelium of the gland, and an increase in the quantity of col- 

 loidal material, that is, to a return toward the normal structure. It is 

 a question whether the symptoms of Basedow's disease are altogether 

 attributable to hyperfunctioning of the gland. The remedial effects 

 of iodine would point rather toward a deficiency of the iodine-contain- 

 ing principle as the origin of the hyperplasia of the secreting epithelium 

 which characterizes the disease. In fact the iodine content of the 

 hyperplastic gland may actually be below normal, and a similar condi- 

 tion may be aroused in the residue by excision of a considerable portion 

 of the gland, as if the effort of a small part of the thyroid tissue to 

 assume the functions of the whole stimulated a proliferation of the 

 epithelial elements. On the other hand it must be recollected that a 

 deficient content of any substance in a secreting gland does not neces- 

 sarily mean that the production of the substance is diminished; it 

 may merely mean that its rate of discharge from the gland is abnor- 

 mally high, so that it has no opportunity to accumulate within the 

 tissues of the gland itself. 



The prevalence of Myxedema and goiter in certain geographical 

 areas and particularly in mountainous or hilly regions, and the com- 

 parative rarity of such conditions elsewhere, has led us to ascribe the 

 endemic forms of thyroid disease, directly or indirectly, to localized 

 physiographical or geological conditions. Even in the days of Marco 

 Polo, the prevalence of Goiter was attributed to a peculiar quality of 

 the water in the localities affected, 1 and this impression still prevails, 

 both in medical and in lay circles. Notwithstanding the clue this 

 offered, however, it has not yet proved possible to establish the nature 



" Departing from thence " (Samarcand) " you enter the province of Karkan . . . 

 The people ... are in general afflicted with swellings in the legs and tumors in 

 the throat, occasioned by the quality of the water they drink." The "swellings in the 

 legs" are attributable to a nematode worm, Filaria medinensis of which the "carrier," 

 or intermediate host, is a minute fresh-water crustacean, Cyclops. 



