Razor. Liquid soap. Cotton-wool. Lysol 2 per cent. solution, in drop bottle. Ether in drop bottle. Flat Hagedorn needles. Blood pipettes (Fig. 16, page 12). Centrifugal machine. Centrifuge tubes. Glass cutting knife. Bunsen flame. Writing diamond or grease pencil. METHOD. 1. Shave the dorsal surface of the ear over the course of the posterior auricular vein (see Fig. 192). 2. Sterilise the skin by washing with lysol. The lysol should be applied with sterile cotton-wool and the ear vigourously rubbed, not only to remove superficial scales of epithelium, but also to render the ear hyperæmic and the vein prominent. 3. Remove the lysol with ether dropped from a drop bottle, and allow the ether to evaporate. 4. Puncture the vein with a sterile Hagedorn needle. 5. Take a small blood-collecting pipette (Fig. 161) and hold it at an angle to the ear, one end touching the issuing drop of blood, the other depressed. The blood will now enter the pipette at first by capillarity; afterward gravity will also come into play and the pipette can be two-thirds filled without difficulty. 6. Hold the tube by the end containing the blood, the clean end pointing obliquely upward--warm this end at the bunsen flame to expel some of the contained air; then seal the clean point in the flame. [Illustration: FIG. 192.--Collecting blood from rabbit.] 7. Place the pipette down on a cool surface (e. g., a glass slide). The rapid cooling of the air in the clean end of the pipette creates a negative pressure, and the blood is sucked back into the pipette, leaving the soiled end free from blood. Seal this end in the bunsen flame. 8. Mark the distinctive title of the specimen (e. g., animal's number) upon the pipette with a writing diamond or grease pencil. 9. When the sealed ends are cold and the blood has clotted, place the pipette on the centrifuge, clean end downward; counterpoise and centrifugalise thoroughly. On removing the pipette from the centrifuge, the red cells will be collected in a firm mass at one end, and above them will appear the clear serum. 10. By marking the blood pipette above the level of the serum with the glass cutting knife and snapping the tube at that point, the blood-serum becomes readily accessible for testing purposes. If larger quantities of blood are required, the animal, after puncturing the vein, should be inverted, an assistant holding it up by the legs. Blood to the volume of several cubic centimetres will now drop from the punctured vein, and should be caught in a tapering centrifuge tube, the tube transferred to the incubator at 37° C. for two hours, then placed in the centrifugal machine, counterpoised and centrifugalised thoroughly. The three most important of the antibodies referred to which can be demonstrated with a certain amount of facility are agglutinin, opsonin and bacteriolysin; and the methods of testing for these bodies will now be considered. AGGLUTININ.