The apparatus which is shewn in figures 10 and 11 consists of a bath deep enough to contain the animal, and a vessel containing the injection fluid. The bath is kept at a temperature of about 110° by an ordinary Bunsen burner. A large Wolff’s bottle (20–40 oz.) with three necks, is fitted with three india-rubber stoppers perforated by glass tubes. Through the central stopper a glass tube connected by a rubber tube, with an ordinary Higginson’s syringe, passes almost to the bottom of the bottle. From one of the other necks a rubber tube passes to an ordinary mercurial manometer, while from the third a tube passes to the flask containing the liquefied injection mass, which is immersed in the water bath. This flask is also firmly stoppered, and should be about half filled with injection material. The delivery tube from the large Wolff’s bottle should only just come through the cork. Another glass tube passes down almost to the bottom of the flask, and is connected by a rubber tube with the cannula inserted into the artery. It will be evident from figure 11 that when water is pumped by the Higginson’s syringe into the Wolff’s bottle the pressure there will be raised (as indicated by the manometer). This increase of pressure will equally affect the air inside the bottle containing the injection fluid, and the fluid will be forced out along the tube and through the cannula into the artery. [Illustration: Fig. 10.--Fearnley’s arrangement for injecting blood vessels. (Reproduced by permission of Messrs. Macmillan, from Fearnley’s _Practical Histology_).] [Illustration: Fig. 11.--Scheme shewing distribution of pressure in Fearnley’s Injection Apparatus (from Fearnley’s _Practical Histology_).] Before using the apparatus a clamp should be placed on the exit tube of the vessel containing the injection fluid, and the pressure should be raised to see that the apparatus is everywhere air-tight. Any leaks should be sealed before the actual injection is commenced. If an isolated organ is to be injected, a cannula of glass or brass should first be inserted into the artery and securely tied in position. The organs, if cold, must be soaked in water at 120° F. for about half an hour and then transferred to a water bath.