FUNDAMENTALS OF MICROBIOLOGY IN RELATION TO CLEANSING 63 branches of medicine by using biological control to eliminate pests. The usual method is to liberate one type of living organism that is predatory on the pest. Little has been done in this direction in industry, although it is well known that by the use of 'starters', e.g. in cheesemaking, undesirable organisms can usually be suppressed. It has been observed in some fields of work that there may be an inverse relationship between the numbers of a harmful and of an innocuous organism. Thus we have observed this type of inverse relationship between Staph. aureus and Staph. atbus in foods, and such a relationship may also be found on the skin. This type of approach to problems of infection is largely an unexplored field. Hygienic packaging The glass bottle is still the favoured container in the cosmetics, milk and other industries, and likely to remain so for some time. Glass is the most hygienic (i.e. most easily cleansed) of all common materials (7) although it is heavy, fragile and susceptible to neglect and sabotage. It has the ad- vantages of transparency, cheapness (if re-used) and does not have to be imported. Blow-moulded plastics bottles are gaining fayour in the soft drinks and other industries. They are very light, cheap, strong, non-fragile, reasonably rigid and initially sterile by virtue of their method of manufacture which involves a temperature of ca. 180øC. Their use is certain to increase. The plastics sachet is the lightest and cheapest of all single service con- tainers, but is experiencing some consumer resistance, as of course do all new ventures. It is likely to be the container of the future for many liquid and solid products. Some progress has been made in the use of sterilizable plastics sachets (ll). General precautions in hygiene, etc. The most efficient cleansing of equipment is easily invalidated if un- hygienic methods are practised subsequently. The following points should be observed: {i) Check the quality of all raw materials. (ii) Unpack raw materials in a separate building, especially if em- bedded in sawdust, cotton waste, straw, etc. (iii) Apply a biocidal treatment where necessary if this is practicable. Controlled heat-treatment is usually the simplest and most reliable.

64 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS (iv) (v) (vi) (vii) (viii) (ix) (x) Control the quality of water as used in the factory. Check the bacterial purity of the air near fillers, etc. Check the hygienic condition of all containers. Remove all residues, broken or split containers, etc., as soon as possible. Do not use cloths for mopping up spillages unless these are main- tained in a clean condition. Such cloths can be a menace. Paper towels are much better (12). Thoroughly clean equipment immediately after use. Sterilize or cleanse all equipment, as may be necessary, immediately before use. Common fallacies in hygiene Some common fallacies experienced in commercial life are the assump- tions that: (i) splashing disinfectant over floors, etc. solves the hygiene problem, (ii) forcing steam through a circuit with the production of great clouds of 'steam' and considerable noise necessarily sterilizes the equip- ment, (iii) if equipment looks clean, then it must be clean. This is not true microbiologically, (iv) 'Window dressing devices' such as making people wear white coats and caps, UV lamps, use of disinfectant aerosols, may serve some useful purpose and undoubtedly exert a psychological in- fluence, but in terms of real worth are not quantitatively very important. Thorough cleaning of all equipment and prevention of contact contamination constitute 99% of factory hygiene. Air Most quality controllers in factories have their views as to how the purity of air should be maintained, both for the staff and the product. An air conditioning system which controls temperature, humidity and removes micro-organisms by filtration and/or electrostatic means is by far the best, but is quite expensive. For the product, as distinct from the staff, an aerosol or fog treatment is the simplest and cheapest, but the choice of biocide is a tricky problem. Chlorine (as hypochlorite) is cheap and effective, but very corrosive.