ENVIEONMENT AMONG MEN 347 



Compared, however, with the state of things among men, and 

 especially in the later stages of history, disease is rare among 

 such species. Among men it comes to assume a peculiar impor- 

 tance. 



Disease results both from the attacks of parasites and from 

 other causes. The various classes of disease will be referred to 

 in the next chapter. We are here concerned only with the 

 results, and we may think of the disease as affecting particular 

 organs in the body and as affecting the general functioning of 

 the organs. Every organ in the body is liable to be attacked 

 by disease and the modifications produced are in many cases 

 familiar. Thus all physical and mental characters may be 

 directly and to almost any degree modified by disease. Again 

 it is known that the result of disease in children is to inhibit 

 growth, and that the growth thus lost is not subsequently made 

 up. Disease may thus be said to draw upon the capital and not 

 upon the income of children.^ We may here confine ourselves 

 to some notice of the effect of disease on the general functioning 

 of the bodily organs which though not so familiar is more important 

 from our point of view. 



The functioning of the bodily organs has been found in late 

 years largely to depend upon certain glands — known as the en- 

 docrinous or ductless glands — in a manner and to a degree alto- 

 gether unsuspected. The thyroid gland, for example, manufactures 

 a secretion which is essential to the proper growth and normal 

 metabolic functions of the whole body. If it is removed from 

 a child, the whole body is stunted and mental deficiency results. 

 Certain maladies, such as goitre, cretinism, and others are known 

 to be connected with a diseased condition of the thyroid. Profound 

 modifications of both physical and mental characters may thus 

 follow when these glands cease to function normally, which is 

 known to be the case in certain specific diseases and may arise 

 in other ways which are not fully understood. 



Temperament depends upon the general functioning of the 

 bodily organs and upon the actual condition of the nervous 

 system. Disease, whether it takes the form of a failure of the 

 ductless glands to function as they should, or some other form, 

 always affects the general functioning of the body and thus has 

 a direct bearing upon temperament. Thus * we know now ', 



1 Galton, Inquiries into Human Faculty, p. 236. 



