THE RESPIRATORY ORGANS 333 



and it is only through the post-mortem examination that the true 

 state of affairs is found. 



543. In a chronic case an animal may go on feeding, thriving, 

 and doing well, and nothing may be observed until it is slaughtered, 

 when masses of tubercular matter are found studded throughout the 

 lungs, liver, and mesentery, some in a fluid condition, others semi-fluid 

 or solid, and enclosed in a capsule, while others are of a cheesy con- 

 sistency or of a calcareous nature. An animal affected like this, when 

 the disease is distinctly localized, I think, might be used for human 

 food ; but when it shows the symptoms of tuberculosis during life by 

 falling off in flesh, though feeding and milking, having a bad cough, 

 being also hide-bound, and with a yellow, scruffy skin — in fact, having 

 all the symptoms of a * piner ' — the sooner it is either buried or 

 cremated the better. 



544. Tuberculosis is due to the tubercle bacilli, and is said to be 

 infectious by inhalation, ingestion, and inoculation. It may be so where 

 animals have a hereditary tendency and have cohabited for some 

 length of time with others thoroughly diseased. Looking backwards 

 for a number of years, I can call to mind one particular bull whose 

 stock — sons, grandsons, and great-grandsons, etc.— have introduced 

 the disease amongst herds where formerly it was never known. 

 Even up to the present day I can put my finger on some of this 

 bull's diseased descendants. This is not an isolated case, for within 

 my own experience I could give many similar illustrations. Strange 

 to say, the malady, in the majority of cases, does not make itself 

 manifest until the animals are coming to puberty (two years old). 

 The same seems to hold good in the human subject. When there 

 are two closely related families, having one mother but two different 

 fathers, or vice versa (the first husband being consumptive, the 

 second being strong and healthy), the children by the consumptive 

 father generally shows signs of the fell disease on their reaching 

 the age of puberty, while the family by the healthy father are hearty 

 and well, without the least symptom of the malady, yet all the time 

 they have been living and sleeping under the same roof and feeding 



