Diaphanography: mechanism responsible for the images.

Preliminary measurements showed that spectrophotometry of samples of tissue taken at operation from the female breast demonstrated no obvious correlation between transmission coefficient and pathology, except that thicker samples tended to transmit less light than thinner samples. However all the samples had absorption minima corresponding to the bands of oxyhaemoglobin. This simple fact led to the speculation that the density of blood in the tissues, (number of red cells per unit volume) was the factor giving rise to different colours of breast tissues and of breast pathology observed upon transillumination with white light in vivo. Examination by infrared colour photography and by spectrophotometry of transilluminated samples of blood diluted with normal saline confirms that the observed colour is dependent on red cell concentration.