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

INHALATION AND TOXICITY STUDIES 403 Device for individual smoke treatment •hort life span but the fact that they have only nasal respiration is a draw- back. It is, therefore, possible to employ also medium-sized animals as, for instance, dogs, pigs, Siamese dwarf pigs, and Rhesus monkeys, if they •vould yield experimental advantages. The general advantages are: 1. The inhaled amounts of gas are comparable to those in humans. 2. The amount of aerosol to be inhaled can be measured relatively easily. It is possible to force the aerosol into the respiratory tract at a rate commensurate with the respiratory rhythm, rather than applying only suction to the respiratory mask. The former gives optimum conditions in respect of any alterations such as ageing of the aerosol. By inserting a tracheal tube connected to suitable valves, it is possible -to automatically record the inhaled and expired amounts of air immediately. EXAMPLES OF EXPERIMENTAL APPLICATIONS It iS worthwhile to mention the possibilities of evaluating lung sections after inhalation toxicity studies. There are the very versatile methods of histochemistry, as an example of which fluorescence-microscopic techniques may be cited.