The virus is accompanied by directions for use which have already appeared in the Zeitschrift für Thier-medicin. These are as follows:
I. Selection of the Animals to be Inoculated.—As a rule only animals without external evidences of disease, from three weeks to three months (for the first inoculation) should be inoculated. In healthy animals of this age a previous tuberculin test is unnecessary, even if the animal comes from a notoriously tubercular herd.
II. Numbering the Inoculated Animals.—Every inoculated animal must be marked with a running number. The marking must be of such a character as to be distinct, not liable to be mistaken for some other, and to last the lifetime of the animal. (Ear-marking, tattooing, etc.) If necessary, the marking is to be repeated should the first mark become indistinct.
III. Keeping of Records.—See under “Conditions governing the distribution of the virus, etc.,” [p. 75.]
IV. Technique of Taking the Temperature.—The body temperature is determined by means of a self-registering thermometer completely inserted into the rectum. Before introducing it, the rectum is to be cleared of any hard fecal masses. A tape about a foot long, having a clamp at its end, is tied to the neck of the instrument. The thermometer is left in the rectum for four minutes, the clamp meanwhile being fastened to the hairs at the root of the tail. In order to save time, thermometers are introduced into a number of animals (about six) consecutively. When the last thermometer has been inserted it will usually be time to extract and read the first. In this way one can take the temperature of fifty head of cattle in 1-1½ hours.
V. The Virus.—The inoculating virus consists of living tubercle bacilli whose action has been accurately tested in the Marburg Institute for Experimental Therapy. The tubercle bacilli have been dried without losing their vital powers in any way. These dry tubercle bacilli (Trocken Tb.), kept in sealed glass tubes, will retain their action on cattle unchanged for a period of thirty days. If, therefore, a tube of Tb. bears the date VII-1-02, the contents can be used for cattle immunization until VIII-1-02. After thirty days, although the immunizing power is not entirely lost, it is so far decreased as to render it ineffective in the dosage recommended.
VI. Dosage of the Virus.—For the first inoculation, one immunizing unit, 1 I. E. [= 1 Immun Einheit] is used for each calf; for the second inoculation, which is not to be undertaken until at least twelve weeks after the first, five units (5 I. E.) are used for each calf. As a rule the dose of 1 I. E. is 0.004 gramme dry Tb., that of 5 I. E. for the second inoculation is therefore 0.02 dry Tb.
If the tube contains the quantity requisite for the first inoculation of twenty cattle, it will bear the label 20 I. E. In order at all times to control the manner of production of the dry Tb. each tube also bears in Roman numerals the consecutive laboratory number thus:
Op. No. IV.
20 I. E.
VII-17-02