mils of 5 per cent aqueous solution of carbolic acid for each 95 mils of blood. The pigs used to produce simultaneous virus must meet the same essential requirements as are met by those used to produce hypering virus; that is, they must show ample evidence that they are suffering with acute hog cholera at the time they are bled, and they must be free of all other infectious diseases transmissible through their blood. Hog cholera virus is sometimes heated at 50° C. for twelve hours before being sent out, in which case a virulence test is necessary before it can be released for field use. In our own work we greatly prefer unheated virus. Keeping qualities. Like protective serum, hog cholera virus must be kept in a dark, cool place. Bureau of Animal Industry regulations allow it to be used not more than sixty days subsequent to the date of drawing, but wherever a thirty-day limit is practicable, we believe it is safer. There are times when an inactive virus may result in as heavy losses as are sometimes charged to impotent serum. Labeling. The virus label should include: 1. Release tag and license number if the laboratory is operated under federal license. 2. Name and address of manufacturing firm or institution. 3. Dosage table. 4. Identification mark, enabling the manufacturer to trace the exact history of any bottle of virus. 5. Return date, or latest date on which the virus may safely be used. 6. Directions for storing. 7. Brief directions for using, and cautions to be observed in destroying unused virus. Hog cholera virus is dangerous material. Onehalf mil or even less will readily kill an ordinary susceptible hog if protective serum is not administered in conjunction with it. Thus hogs given simultaneous treatment in the field actually receive, as a routine measure, a lethal dose of virus. It is really remarkable that this practice results in so little trouble, but potential danger, slight though it is, exists whenever virus is used, and this fact should be well understood both by the veterinarian and his client. Under no circumstances should virus be used by untrained men. CHAPTER VIII METHODS OF USING ANTI-HOG-CHOLERA SERUM Confining the animals. We will consider first methods of confining the animals to be treated. To one unaccustomed to handling hogs the task of confining and vaccinating a large herd of swine seems formidable, and not infrequently the difficulties presented, although largely imaginary, have led to costly neglect or procrastination. Chasing hogs to catch them is usually futile, it is time consuming, and if double treatment is to be applied, or if the animals are fat, the practice is positively dangerous. Ingenuity is required, and the veterinarian who can use the help and materials at hand to best advantage, enabling him to vaccinate a herd quietly and rapidly, and without exciting the animals, gains much in the confidence of his clients. If the time that vaccinating is to be done is known to veterinarian and client the latter should tempt the animals into pens or small enclosures with feed and fasten them in securely. Bedding should be provided so that the hogs will be clean and dry. In cases of emergency, where this ad vance knowledge is lacking hurdles should be used to crowd the animals into the corner of a yard or PLATE 14. Injecting anti-hog-cholera serum in the ham pasture. In all cases in which fences are insecure it is important to mark each animal at the time it is vaccinated, so that if treated and untreated ones should accidentally get together identification will still be possible. Paint, chalk, bluing or tincture of iodin are convenient for this purpose, or if a PLATE 15. Method of holding shoat for injecting permanent mark is desired, the ear may be notched. Assuming that the animals are fastened in small pens when the veterinarian arrives, confinement of the individual during the process of immuniza |