834 MICROBIOLOGY OF DISEASES OF MAN AND DOMESTIC ANIMALS 



phthisis (tuberculosis of the lungs). It also frequently appears in the 

 mesenteric glands and other glands of the body, and may appear in any 

 of the tissues. It is quite possible, judging from autopsies, that many 

 persons have tuberculosis without realizing its existence in the body, 

 and without its being detected in any way. It is questionable, how- 

 ever, whether under such circumstances the disease is transmitted or 

 disseminated. 



As a rule affected cattle show no definite outward signs of the dis- 

 ease. Badly diseased animals sometimes appear poor and unthrifty. 

 Many cases are mild and latent. A few tubercular animals cough; 

 some show harsh hair and skin and other expressions of ill health. 

 While these symptoms do not necessarily indicate tuberculosis, they 







are very suggestive. 



Bad. tuberculosis may invade almost any tissue or organ of man or 

 the animal body and produce a variety of lesions. Man usually gives 

 some evidence of the disease either objectively or subjectively, and in 

 many instances the disease assumes a definite form which is easily rec- 

 ognized by medical men, unlike its presence in animals. The symp- 

 toms are more evident in swine than in cattle. Affected hogs are often 

 unthrifty and show glandular enlargements and degenerations of the 

 enlarged glands. 



Avian tubercle bacteria are becoming disseminated among poultry, 

 and to a serious extent in some sections of the country. Among the 

 more prominent symptoms of avian tuberculosis are emaciation with 

 marked anaemia and weakness. Examination of the carcass shows dis- 

 ease most frequently in the liver, but intestines, spleen, lungs, and even 

 the skin may be invaded. Danish authorities report* serious outbreaks 

 among swine due to avian tubercle bacteria. 



It has long been firmly established that Bact. tuberculosis is the spe- 

 cific cause of this disease. But while this bacterium is to be regarded 

 as the specific cause it must be understood that this organism is fre- 

 quently associated with pus-producing bacteria which are responsible 

 for certain phases of the disease as commonly seen. It should be under- 

 stood also that persons and animals become more susceptible and have 

 greater opportunities for infection under close confinement and lack of 

 exercise. There has been great difference of opinion concerning the 



* Dunne, Trans. Jour. Bd. Agr. (London), 22 (1915"), No. i. 



