INHALATION AND TOXICITY STUDIES 401 E. ' ,f Figure 3 Testing chamber If administration to individual animals is desired another experimental device (Figure 5) developed in our laboratories can be used. Every animal is fixed in this device after the appropriate acclimatization to these conditions. The test material is administered to each animal in- dividually by means of a pharyngeal or tracheal probe, or through a mask, the duration and frequency of the application can be regulated centrally. This apparatus is valuable for testing the effectiveness of pharmaceuticals. which are absorbed as aerosols via the mucous membrane of the mouth or respiratory tract. In such experiments the test aerosol must enter the respiratory tract as unaltered as possible, and it is essential that the mount can be measured very accurately. Often it is impossible to select a definite species of animal without preliminary trials. Nor is it advisable to restrict the tests to only one species. The small rodents, for instance, offer the advantage of a relatively

402 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS Lamp Thermostat • Motility Temperature cat Recording --Digit Read Motors Digital Indicators Diagram ooe respiration apparatus a Animal holder f Membrane condenser b Membrane pumps g Urine collecting vessel c Flow regulator h Flowmeter d CO s absorption i Humidity regulator e O, compensator k Resistance thermometer