THE GOITROUS ENLARGEMENT. 739 



and cells resembling the uniform epithelial-like layer. The arteries, 

 four in number, and of considerable size, end, between and upon the 

 walls of the vesicles, in a close capillary network, which empties itself 

 into the veins. The lymphatics are numerous and large; their rela- 

 tions to the structural elements of the thyroid body are unknown ; but 

 it is supposed, from their relative size and abundance, that they are 

 more concerned in returning the contents of the thyroid vesicles to the 

 blood, than the lymphatics of the suprarenal bodies, or spleen, are, in 

 regard to those organs. 



Enlargement of the thyroid body constitutes the disease known as 

 goitre, in which the condition of white blood, leucocythsemia, or leu- 

 caemia, is often induced. In such cases, the nucleated cells of the 

 thyroid body, and their contained nuclei, are smaller than usual, and, 

 a fact of much interest, the white corpuscles of the blood are not only 

 more numerous than in health, but are also unusually small. This so 

 far favors the view, that the thyroid body may aid in the formation of 

 the morphological constituents of the blood. 



The thyroid body may also influence, like the other ductless glands, 

 the chemical composition of the circulating fluid. The chief constit- 

 uent of the glairy fluid of the thyroid vesicles, is of an albuminoid 

 nature ; but, unlike the splenic pulp, it contains a noticeable quantity 

 of fatty matter. Its extractives and salts differ in no important par- 

 ticular from those of the blood. 



Some physiologists have supposed that the thyroid body acts me- 

 chanically, as an occasional diverticulum for the blood concerned in 

 the cerebral circulation ; but the evidence of this is even less than that 

 adduced on behalf of a similar hypothesis concerning the spleen and 

 the portal circulation. 



The goitrous enlargement of the thyroid body, which produces such unsightly 

 disfigurement of the neck, is most frequently met with in females. It prevails 

 in particular countries, and in particular districts of those countries. Thus, 

 it is met with chiefly in the north of Italy, and in certain cantons of Switzer- 

 land, most markedly in the canton of the Valais. In other European coun- 

 tries, it is met with much less frequently ; but still asserts a preference for 

 particular districts. In England, it is most common in Derbyshire, and hence 

 its popular name, the Derbyshire neck ; but it is observed in many other scat- 

 tered localities. In spite of careful investigations, involving researches into 

 the climate, solar influence, atmospheric peculiarities, rain-fall, soil, and 

 drinking-water of those districts, and into the manifold conditions of existence 

 of the people, the true cause of goitre has not yet been inductively ascertained. 

 It is more common in the country than in towns, and is almost entirely con- 

 fined to hilly and mountainous districts, being more particularly observed in 

 the valleys of those districts ; but it is not prevalent in all elevated or moun- 

 tainous regions. It has been variously attributed to the deficiency of oxygen 

 in the higher levels of the atmosphere ; to the want of solar light in valleys, 

 especially since, as is alleged, it prevails more on the southern, and compara- 

 tively sunless, sides of such valleys ; to the habitual use of drinking-water 

 derived from the melting of glaciers or of snow, and therefore almost entirely 

 destitute of saline and earthy salts ; and, again, on the contrary, to the pres- 

 ence of lime, but particularly of magnesia, in such water, derived from the 

 limestone or rnagnesian limestone, often found in districts in which goitre is 

 common. Lastly, its special prevalence amongst females, has been assigned 

 to the custom, in hilly districts, of carrying water, or other heavy substances, 



