• Chapple. — On Tuberculosis in Man and Animals. 527 



ment in practice, than lias resulted from the cures of a 

 century. 



Of all the diseases which come within the province of pre- 

 ventive medicine none bulks so largely in national importance 

 as tuberculosis. Tuberculous diseases are the scourge of the 

 British Isles, where scarcely a family is to be found that has 

 not suffered directly or indirectly from this insidious foe. All 

 civilised countries in temperate regions are afflicted by its 

 ravages. It attacks its victims in the bloom of youth or in the 

 flower of manhood, while those who are marked for its prey 

 often show a clearness of intellect, a vivacity of character, and 

 a loftiness of conduct much above the normal, making this 

 disease responsible for the aphorism that " the good die 

 young." 



Since Koch's discovery in 1882 of the bacillus of tubercle 

 a complete revolution has taken place in our knowledge of 

 tuberculosis. It is now held to be, and treated as, an in- 

 fectious preventible disease, whose manifestations vary with 

 — (1) the animal attacked, (2) the organ attacked, (3) the 

 degree of infection. 



The cause of the disease is a minute vegetable organism 

 belonging to the Schizomycetes, and known as the Bacillus 

 tuberculosis. It is rod-shaped, Tf-^^Qva.. in length, and developes 

 by the formation of spores. It flourishes best in dead or 

 partially devitalised animal tissue, but when the disease is 

 prevalent it abounds almost everywhere. The expectoration 

 of a tuberculous man or animal contains millions of these 

 organisms and their spores. After drying on pavements, 

 floors, walls, or grass, the germs are carried about in the air, 

 which is inhaled by others, or the grass may be eaten by 

 stock previously free from infection. The presence of this 

 minute organism in any of the body-tissues then constitutes 

 tuberculosis ; its absence makes the existence of the disease 

 impossible ; and it is this organism that has to be reckoned 

 with in all public - health measures for the control of 

 consumption. Kest, warmth, moisture, and nutriment are 

 required in partially devitalised, non-resistent, or weakened 

 animal tissue, to allow of a nidus being formed for the develop- 

 ment of the bacillus. These conditions are found in the tops of 

 the lungs of young people who restrain the functional activity 

 of these areas by cramping the chest, especially if there is a 

 constitutional weakness of the lung-tissue due to the disease 

 having existed in the parents. In this sense only, it might 

 here be remarked, is tubercular disease hereditary ; the 

 constitutional or tissue weakness is transmitted, and these 

 weakened body-tissues become an easy prey to the invading 

 bacillus. There is no direct transmission, though there may 

 be maternal infection, and the child die in infancy. 



