(Following is an abstract of a public lecture on "How Accidents Happen" given at the Harvard Medical School yesterday by Dr. Henry C. Marble, Assistant in Industrial Hygiene at the School of Public Health.)

The history of accidents shows that up until quite recent times accidents were generally considered to be Acts of God--that is, accidents just happened and nothing could be done about them. But today, efforts are being made to lower the number of accidents, for nowadays it is recognized that there are quite definite factors, the quality and degree of which determine the occurrence of the accident and the extent of the injury received in the accident. These factors, or steps, may be summarized as follows.

In the first place, the inheritance and environment of the person involved is important. For instance, a person who is known to be mentally and physically slow should not be put to work in a position where quick reaction is needed, where a crisis might arise requiring quick judgment and action. Then in the second place, the mental and emotional factor must be taken into consideration. Under this category come such things as fear, anger, worry, inattention, all those things which tend to distract a person from the task in hand. With these two as a basis, there is a third factor, which we call the mechanical factor. By this is meant some mechanical obstruction, some physical hazard, or some unsafe condition. As an illustration, we might imagine a man driving on the wrong side of the road. Now, this he might do for an hour or so without having an accident if there were no other traffic on the road; it is only when he encounters some other vehicle--some "obstacle"--which he cannot avoid hitting that an accident, the fourth step in the series, occurs. The fifth factor may be called the "momentum" or "force" involved, upon which depends the extent of the injury. This same order of factors applies to all sorts of accidents.

A great deal of effort has been made to control factors 1 and 2, to make environmental factors more ideal for safety and to eliminate fear, worry, and so forth. In regard to factor 3, safety organizations have ben set up to take out the mechanical factors--i.e., in shops, to make the machinery and the working conditions safer--so that step 4, or the occurrence of accidents, may be minimized and so that step 5, the extent of injuries, may be lessened. But the degree of control which has been achieved differs quite widely according to the type of accident. In the home, for instance, there is little or no control over the types of people who are about the house, and mental attitudes are not easily regulated; physical hazards, such as stairways without railings, defective wiring, highly-polished floors, have not been consistently done away with, so that accidents which happen may be very severe. In the automobile, a sufficient amount of care is not used in the choice of who is to be allowed to drive. Here, personal characteristics play a leading part and the mental factor is very important.