310 
Tuberculosis in Animals, and 
ever may be the part played by debilitating influences in 
the production or progress of tuberculosis, Dr. Ransome has 
recently shown that, among people in communities where such 
influences ai'e general and continuous, consumption is far more 
prevalent than in others where such influences are not at work, 
and he explains that debility, induced by whatever cause, appa- 
rently renders the body more susceptible to the invasion of dis- 
ease-producing organisms and likewise prepares it as a suitable 
soil, so to speak, for their proper growth and multiplication. 
Heredity has always been looked upon as a cause of 
tuberculosis, but this has, as already stated, been the result of 
practical observation rather than of scientific inquiry. It is 
difficult to say in what way heredity operates as a cause of 
disease. It may possibly be on the generally accepted principle 
that like produces like, and in this case the consumptive off- 
spring of consumptive parents is only an example of a general 
natural law. On the other hand, direct infection may occur 
before birth ; the tubercle bacillus may be transferred from the 
parent to the foetus. Professor Johne, of Dresden, found in an 
eight-months' calf caseous nodules containing tubercle bacilli : 
it has also been said that the organism may be transferred to 
the ovum at the time of impregnation. 
In connection with the question of the hereditary trans- 
mission of tubercle, breeding in and in has long been accepted 
as an important factor ; but that view is no longer tenable in 
face of the evidence which can be furnished by well-known 
breeders of pedigree stock. Breeding in and in, so long as 
healthy stock are used, will never produce tuberculosis, but if 
tainted animals are used for the in-breeding, then the hereditary 
taint will be more and more intensified. Hence it is evident 
that the introduction of one tuberculous animal into a breeding 
herd may cause incalculable and almost irreparable misdhief if 
not speedily discovered and the mistake corrected. 
Until quite recently it was generally accepted, that of our 
domesticated animals cattle were the only victims of this disease, 
and, therefore, the only ones from which man might become 
affected through the use of their flesh as food ; but it is now 
known that fowls are more frequently attacked than any other 
animals. Experiments have shown that rabbits and guinea-pigs 
are also very susceptible. Pigs are not uncommonly affected, 
sheep and goats are occasionally attacked, and the malady now 
appears to be more common in tho horse than was suspected 
only two or three years ago. Carnivorous animals are compara- 
tively free from any tendency to tubercular infection, but, 
although they evidently enjoy a considerable amount of im- 
