628 MICROBIOLOGY OF THE DISEASES OF MAN AND ANIMALS. 



of the skin), or scrofula (tuberculosis of the cervical glands), or 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. 

 Open tuberculosis in man is quite easily recognized, but when it is concealed 

 it becomes difficult to diagnose its presence. It is quite possible, judg- 

 ing from autopsies, that many persons have tuberculosis without realiz- 

 ing its existence in the body, and without its being detected in any way. 

 It is questionable, however, whether under such circumstances the 

 disease is transmitted or disseminated. 



As a rule affected cattle show no definite outward signs of the disease. 

 Badly diseased animals frequently appear fat and thrifty. Bact. tuber- 

 culosis does not, as a rule, produce an evident disease. 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. 



Bact. 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 not necessarily objectively but 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 symptoms 

 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 

 disease most frequently in the liver, but intestines, spleen, lungs, and 

 even the skin may be invaded. The avian tubercle bacterium varies in 

 certain respects from the bovine variety; it usually measures from i/t to 

 4/j. in length with a general average of 2.77*. 



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

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

 specific cause it must be understood that this organism is frequently 

 associated with pus-producing bacteria which are responsible for certain 

 phases of the disease as commonly seen. It should be understood also 

 that persons and animals become more susceptible and have greater 

 opportunities for infection under close confinement and lack of exercise. 



