The Effects of Biological Tissues on 15-mc Pulsed Ultrasound

The subject of this paper, which is mainly descriptive, grew out of the desire of a biologist to measure the thickness of the human bowel wall in the living intact subject. [J. J. Wild, Surgery 27, 183 (1950)]. The object was to justify certain methods of treatment for the suspected underlying mechanisms at work, the results of which are lumped together by surgeons under the title of bowel distension. The approach to the subject has been almost entirely biological, not ignoring, however, the theory of sound where applicable. It will be seen that biological methods of control are used as a first approximation in order to justify more detailed examination of the system. Some of the difficulties of the exact approach from theory will be discussed after presentation of the experimental facts. It may be of interest to the more exact-thinking members of the audience to note that a system having a nightmare of complexity to the physicist may be considered simple by the biologist in his blissful ignorance. This situation is perhaps fortunate because otherwise the biologist might be tempted to give up too easily. It is the duty of the biologist to try to simplify complex phenomena so that his more able colleagues in more exact branches of science will be stimulated to “pitch in” and help. We hope that today we shall be able to bring about this desirable end and succeed in stimulating more workers to investigate this field. It should, however, be realized at the outset that the increasing exploitation of the observed phenomena does not necessarily need to wait upon whatever fundamental explanations may be forthcoming. The experimental results will not necessarily be presented in chronological sequence but an attempt will be made to present some of our collected experimental data in as logical a manner as possible.