Ingestion of asbestos.

Several papers at this conference have dealt with studies' of ingestion of asbestos in one form or the other. 'In one experiment, following asbestos ingestion, a gastric ulcer with an asbestos fiber perforating it was observed. One investigator did not 'find any significant pathology in the gastrointestinal tract with ingestion of asbestos, and some other workers found few particles here and there. I suggest that one of our most urgent needs is a proper and suitable choice of an experimental animal. In my opinion, the rat is one of the animals that should not be used. The simple reason is that half of the rat's stomach is lined by squamous epithelium and therefore does not simulate the human stomach. Dr. Shay from the United States (1) has been using rats to produce gastric ulcers which are not at all similar to those'found in humans. The ulcers developed in rumenal mucosa which is lined by squamous epithelium. A second difficulty is collection of gastric juice. I do' not know of much work that has been done with small intestine-or for that matter, with cecum and colon. I think that the monkey is a difficult animal to deal with. The fact that it is vegetarian also presents difficulties. You always find some food particles in the stomach-there is always some roughage left over. Therefore, if we have to do work on stomach or for that matter on intestine, we should not use monkeys. Now let us take th,e rabbit. Twenty years ago, I did some experiments on rabbits. I kept them without food for 4 days, put them on water and after 3 or 4