TUBERCULOSIS 127 



COW which had been kept in the form of a dried powder for 

 five months, but they found in this particular case that at a 

 later date the virulence was lost. 



The ability of the bacillus of tuberculosis to form spores, 

 and the obstinacy with which they retain their vitality in 

 dried sputum, amply compensates for its inability to grow 

 outside the body (except on special media), and makes it 

 the most fatal and prevalent disease in these Northern 

 climates. In observations and experiments made inde- 

 pendently in Germany, Italy, and France by Kossal, 

 Brouardel and Picini, the disease was found latent, post- 

 mortem, in forty to sixty per cent, of persons who had 

 disclosed no symptoms during life. 



Pathogenesis. — Localised tubercular affections may occur 

 in almost every part of the body. The bacilli or spores, 

 having been inspired and entering into the circulation, 

 invade the weakest part. A local traumatic injury may 

 thus determine the onset of the disease in that portion of 

 the body affected. Many diseases predispose to phthisis, 

 as, for example, whooping-cough, pneumonia, diphtheria, 

 scarlet fever, typhoid, syphilis, etc. It is observable that 

 in the' case of hospital patients at least 50 per cent, will , 

 be found to have a tubercular history. The bacillus has 

 occasionally been found in the foetus, but not often enough 

 to afford evidence that hereditary transmission is common. 

 When we consider, however, that, as above stated, quite 

 50 per cent, of patients have a phthisical history — that is 

 to say, are born of those already weakened by the disease, 

 and have, perhaps, been brought up in an atmosphere 

 teeming with the specific virus — it does not seem hard to 

 account for the run of the disease in families, or, as is 

 sometimes noticed, in particular habitations. The warty 

 excrescences which sometimes follow post-mortem wounds, 

 and are apt to appear on the hands of those often occupied 



