Bovine tuberculosis : cause, cure, and eradication a summation of material, facts and eminent opinions for the use of farmers, cattle-owners, milk-producers, veterinarians, students, and others with appendices on the diseases which simulate tuberculosis, actinomycosis and Johne's disease also appendices on calf mortality and the destruction of rats, and a glossary of technical words.

Date:
[1912?]
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Licence: In copyright

Credit: Bovine tuberculosis : cause, cure, and eradication a summation of material, facts and eminent opinions for the use of farmers, cattle-owners, milk-producers, veterinarians, students, and others with appendices on the diseases which simulate tuberculosis, actinomycosis and Johne's disease also appendices on calf mortality and the destruction of rats, and a glossary of technical words. Source: Wellcome Collection.

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    Instability ol type action of the products of their own growth, and unless removed frequently to fresh nutriment will gradually weaken and die. “ Since, then, it must be admitted that there are many forms of pathogenic micro-organisms that can be materially altered by increase of heat to their surroundings, by the application of the direct rays of sunlight, by increasing or decreasing the acidity or the alkalinity of their nutriment, by the influences of the products of their own growth, and by passage through animals either susceptible or resistant to their action, is it too much to suppose that tubercle bacilli may also be altered in form, virulence, and in vigour of growth, when cultivated under unusual conditions ? Experiments have shown that some tubercle bacilli may be transformed in form, pathogenicity, and cultural characteristics as well. More than this, cultures which seem incapable of attacking certain species of test animals with the degree of severity which one would expect in view of their average virulence for animals of other species, may be brought to change their peculiar affinities until they prove virulent for a species of animal formerly resistant.” “ That these two types stand very near to each other,” says Theobald Smith,1 “ cannot but force itself upon the attention of all who study them at close range. We know that they have a common toxic basis in tuberculin, and probably come from a common ancestor ; but the question whether the two types have become so specialised by adaptation to different hosts as to have lost the capacity for being transformed one into the other is still unanswered.” The British Royal Commission made a number of attempts to transmute the bovine bacillus into the human bacillus, and vice versa. “ Most of these attempts failed altogether, a few only were equivocal ; we found indeed,” the Commissioners2 continue, “ that under the conditions contrived by us, both types of bacilli remained remarkably stable, alike as regards their growth on artificial media and their virulence for animals. Thus, we are inclined to regard transmutation of bacillary type as exceedingly difficult if not impracticable of accomplishment by laboratory procedure, though in view of certain instances in which we obtained from one and the same human body both types of bacillus, we are not prepared to deny that the trans- mutation of one type into another may occur in nature.” According to Park and Krumwiede, Junr.,3 “ Damman and Mussemier claim to have completely changed the type of a sputum culture by passage through goats. They used five goats, and give the impression of a gradual change which is not proven by the facts. “ De Jong reported a like increase in virulence after residence in a goat for three years and 145 days.” 1. 6th I. C. on T., Vol. 4, pt. 2, p. 663. 2. Final Report, p. 30. 3. Collected Studies from the Research Laboratory, Department of Health, City of New York, Vol. 6, p. 119.