Human Physiology. j6j 



to arise spontaneously, but is propagated as a special virus or 

 distinct contagion. 



Tubercular diseases, as scrofula and consumption, though to 

 some extent hereditary in their character, seem less mysterious 

 in their origin, or determining causes, than those generally 

 recognised as contagious. They prevail in some climates, 

 countries, and races more than in others. The purer races 

 like the French, Spanish, and Italians are less liable to 

 scrofula and consumption than the mixed races of Germany, 

 England, and America. The people of cold and damp climates 

 suffer more than those of warm and dry ones. Consumption is 

 more frequent in the North-eastern States of America than in the 

 South-western, while the dry, equable climates of Texas, New 

 Mexico, and California, are almost free from it. Spongy, or 

 clayey soils, with their cold and dampness, favour its develop- 

 ment Bad air and the absence of light are evident causes oF 

 tuberculous diseases. Insufficient nutrition, and the milk and 

 flesh of tuberculous animals, are also probable causes. Scrofula, 

 king's evil, white swelling, and consumption, are undoubtedly 

 hereditary, whether original diseases or modifications of syphilis. 

 Consumption of the lungs seems to be a direct consequence of 

 this protean poison. In the regiments of the British army most 

 exposed to syphilis, half the men die of consumption. There 

 is also much reason to believe that the tuberculous predisposi- 

 tion to the disease itself may be propagated by contagion. 

 Animals inoculated with tuberculous matter have developed 

 tubercles, and consumption has prevailed in camps and 

 barracks to such a degree that the surgeons were forced to 

 the belief that it was communicated from man to man, 

 probably by the inhalation of the matter of the disease. Con- 

 sumption is a common disease of habitual drunkards, and 

 of persons of disorderly lives and exhausted vitality. It 

 therefore seems probable that when the impurities of the 

 body, from any cause, cannot be cast out, they gather int 



