The Journal of the Department of Agriculture, Victoria . e that has been touchedb\ the needle. The growths that result—or. as they-are termed. cuUtures —have, in many cases, characteristic appearances, which assist 494 journal of Agriculture, Victoria. [lo Aug., 1912. considerably in arriving ai a correct diagnosis. Tliis culture method cango on through many generations, and though the first may be some-what mixed—that is to say, contain more than one distinct organism—it is possible by sub-cultures to eventually obtain a perfectly pure cultureof the organism concerned. Microscopical examinati
The Journal of the Department of Agriculture, Victoria . e that has been touchedb\ the needle. The growths that result—or. as they-are termed. cuUtures —have, in many cases, characteristic appearances, which assist 494 journal of Agriculture, Victoria. [lo Aug., 1912. considerably in arriving ai a correct diagnosis. Tliis culture method cango on through many generations, and though the first may be some-what mixed—that is to say, contain more than one distinct organism—it is possible by sub-cultures to eventually obtain a perfectly pure cultureof the organism concerned. Microscopical examination of these culturesfrom time to tme will reveal the organism originally inoculated into thetube. They may be also grown on plates (Fig. 9). In order to provethat a micro-organism is the cause of a , it is necessary (1) thatthe organism in question, as recognised by its form, mode of grovvth, orproducts, be found constantly associated with the disease at least in theearlier stntres nnd in sufficient numbers to account for he svmptnms;.. A. Mature female and egg^. B. Hide showing cattle ticks. C. Various stages of cattle ticks. (2) that pure cultivation of thi;organism through sufficient generations be made, until it masreasonably be .supposed thaeverything else which couhpossibly have been taken fronthe animal that yielded thiorganism has disappeared . (3) that other susceptible animabe inoculated with the culti-vated organism, and that be reproduced ; (4) thatthe same organism be found inthe tissues of the successfully inoculated animals in such numbers,and with such a distribution, as to account for the disease. Inmany cases it is necessary for the organism which produces diseaseto be transferred from one animal to another by means of inter-mittent hosts, such as biting flies, ticks, mosquitoes, fleas, &c. (Figs. 10, 11);as an example, the disease known, at any rate by name, to nearly all, as Texas or Tick Fever in cattle. This is caused by a sma
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Keywords: ., bookcentury1900, bookdecade1900, booksubjectagricul, bookyear1902
