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 | +-------------+ This label is interpreted as follows: Dry Tb., which in the records of the Marburg Institute bears the laboratory number IV, contain on the day of delivery, i.e., on VII-17-02, twenty immunizing units, and retain this strength until VIII-17-02. For the inoculation the virus is uniformly mixed with 1% salt solution which has previously been boiled and cooled. The procedure is as follows: