Fig. 3.
Trichinæ Capsulated in Flesh.
Magnified.
(3) Tuberculous Meat, from animals suffering from tuberculosis, has been found to cause tuberculosis in small animals experimentally fed on it. Koch has recently thrown doubt on the communicability of bovine tuberculosis to man; but this point must be regarded as still unsettled (see page [312]). Sheep are rarely affected by it, but it is very common in cattle, especially in cows, and it is a serious economical question whether the meat of all such animals should be condemned. The ideal would be to condemn all such animals, as tuberculosis is an infective disease, and the bacillus which causes it (as well as the toxic products of its activity) may be present in meat which shows no actual signs of disease, except in the lungs or other internal organs. In practice, however, the rules laid down by the Royal Commission on Tuberculosis, in 1898, should be followed for the present. These state that:—
“The entire carcase and all the organs may be seized (a) when there is miliary tuberculosis of both lungs, (b) when tuberculous lesions are present on the pleura and peritoneum, or (c) in the muscular system, or in the lymphatic glands embedded in or between the muscles, or (d) when tuberculous lesions exist in any part of an emaciated carcase. The carcase, if otherwise healthy, shall not be condemned, but every part of it containing tuberculous lesions shall be seized (a) when the lesions are confined to the lungs and the thoracic lymphatic glands, (b) when the lesions are confined to the liver, (c) or to the pharyngeal lymphatic glands, or (d) to any combination of the foregoing, but are collectively small in extent.” They also add that any degree of tuberculosis in the pig should secure the condemnation of the entire carcase, owing to the greater tendency to generalisation of tuberculosis in this animal; and that in foreign meat, seizure should ensue in every case where the pleura has been “stripped.” (See also page [312].)
(4) Other Infective diseases besides tuberculosis may render meat wholly or partially unfit for food. Of these pleuro-pneumonia may not require condemnation of the entire carcase; but in the following this course should be adopted, cattle-plague, pig typhoid (pneumo-enteritis), anthrax, and quarter ill, as well as in sheep-pox. In puerperal fever, actinomycosis, and sheep-rot (liver flukes) each case must be decided on its merits.
II.—Decomposed Meat.—Putrid meat has often produced diarrhœa and other severe symptoms. Putrid sausages are especially dangerous, and incipient putridity seems to be more dangerous than advanced.
Tinned Meats occasionally produce severe illness, which has been in several cases fatal. It is important to secure a good brand, and to eat the meat as early as possible after the tin is opened. Tins in which any bulging is present, showing the presence of putrefactive gases, must be rejected; and still more tins which have been pricked and resoldered in a second place. All tinned meats and fruits are stated by Hehner to contain compounds of tin in solution. These do not seem to be perceptibly injurious, unlike lead salts, which are now rarely found.
The general subject of Meat Poisoning has had much light thrown on it during the last few years. Brieger, about 1886, showed that during the cultivation of bacteria, alkaloidal bodies known as ptomaines and leucomaines, were formed, which were virulently poisonous. It was commonly supposed that the poisoning occasionally produced by eating meat pies, sausages, hams, brawn, and similar food, was due to these ptomaines. It is now known, however, that there are far more important toxines than the alkaloidal, which result from bacterial life in meat, etc. (see page 286). These are more closely related to substances of an albuminous or proteid nature than the ptomaines. These toxines may be fatal when as small a dose as a fraction of a milligramme (mgm. = about 1 ∕ 64 grain) is given subcutaneously. The evidence now shows that neither ptomaines nor other toxines (albumoses) or any other bacterial products besides these, cause the outbreaks of acute poisoning occasionally traced to food, but that these are due to bacteria. There is, in other words, actual infection, as well as poisoning. The microbe chiefly found as the cause of these outbreaks is the Bacillus enteritidis of Gaertner, and some allied microbes. In an outbreak at Oldham, 160 pies made on a Thursday, from the veal of a calf killed on the preceding Tuesday, were baked in several batches, and of the persons eating these pies fifty-four became ill. That the contamination was not introduced after cooking was shown by the fact that several persons were made ill who ate pies still warm from baking. The facts indicated that one batch was imperfectly cooked, the time allowed being only twenty minutes, as compared with fifty minutes allowed in corresponding cooking in domestic life. Experimentally it has been found that an exposure for one minute to 70° C. kills the Bacillus enteritidis of Gaertner. That this bacillus was the cause of the outbreak was subsequently shown by the fact that the serum of blood taken from some of the patients showed characteristic clumping with a pure culture of this bacillus, just as happens with the blood of a patient suffering from enteric fever when a cultivation of the microbe of this fever is mixed with it (see page [301]). In this outbreak the symptoms were usually diarrhœa, vomiting, intense thirst, desquamation of the skin, and a slow convalescence, lasting from three to six weeks. (See page [26] for poisoning by Bacillus enteritidis sporogenes.)
III.—Meat injuries from the food eaten before killing.—Pheasants fed on laurel, hares on rhododendron chrysanthemum, and other animals fed on the lotus, wild cucumber, and wild melon of Australia, have caused dangerous symptoms.
IV.—Fish, especially some kinds, occasionally produce nettlerash and other disorders, especially in warm weather. Leprosy has been ascribed to the eating of decomposing fish, but it occurs in countries where a fish diet is impossible.
Shell-fish and crustaceans (as lobster, crab) are very prone to produce evil results. Shell-fish (mollusca), such as mussels, cockles, and oysters, are dangerous foods. They are generally grown in estuaries, to which the sewage of towns has access; and not infrequently cases of enteric (typhoid) fever, as well as more acute attacks of diarrhœa and vomiting, have been traced to them. Mussels and cockles are seldom sufficiently cooked to render them safe; and oysters are eaten raw. They should never be eaten, unless from personal direct knowledge it is certain that they have been derived from an estuary in which there was no possibility of contamination by sewage.