Discharges of whatever kind should likewise be collected in sterile receptacles and examined as soon as may be.
If internal organs are to be examined it is best to kill a moribund animal than to wait for death, since after death, and in severe infections even sometimes before, the tissues are rapidly invaded by saprophytic bacteria from the alimentary and respiratory tracts which complicate greatly the isolation of the specific organism. Hence the search for specific bacteria in carcasses or organs several hours after death is frequently negative. Animal inoculation with such material is very often followed by sepsis or septicemia in a few hours, so that the specific organism has no opportunity to manifest itself.
In securing material for cultures from internal organs it is a good plan to burn the surface of the organ with a gas or alcohol flame, or to sear it with a hot instrument to kill surface organisms, then make the incision or puncture through the burned area and secure material from the interior of the organ. Such punctures made with a stiff platinum needle frequently give pure cultures of the organism sought. Slides may be made from such material and culture media inoculated at once.
Since a bacteriological diagnosis depends most commonly on growing the organisms, it is evident that material sent for examination must never be treated with an antiseptic or preservative. If decomposition is to be feared the only safe procedure is to pack the material in ice and forward in this way.
Tuberculous material from the parenchyma of internal organs may be forwarded in a preservative (not formalin, since this makes it very difficult to stain the bacteria) as in this special case a very positive diagnosis may be made by staining alone. Even here it is better to pack in ice in order that the diagnosis by staining may be confirmed by inoculating the living organisms into guinea-pigs.
In the case of material from a rabid animal and many protozoal diseases the rule against preservatives is not absolute, since staining is a reliable diagnostic means. Even in these cases it is often desirable to inoculate animals, hence, as before stated, it is best to make it a uniform practice to pack material for examination in ice and use no preservatives.