Oncography

ONCOGRAPHY, a method for studying blood circulation in internal organs of animals by measuring the volume of these organs with the so-called oncograph. For recording fluctuations of peripheral organs (limbs), a plethysmograph is used (see Plethysmography). The oncographic apparatus consists of an oncograph, a transmission device, and a recording device. The transmission device is a rubber tube, and the recording device is Marey's drum, a piston-recorder, etc. There are many different designs of oncographs depending on the organ being studied. The best-known oncographs are for the kidney (Roy's), for the spleen (Schefer's), for the intestines (Edmunds'), for the heart (Henderson and Külb's), for the lung (Dixon's), for the brain (Gottlieb's), and others. Every oncograph is a rigid capsule shaped to fit the organ with which one wishes to work. After the organ is exposed surgically, it must be placed in the oncograph in such a way that the dead space is, on one hand, constant, and on the other hand, the oncograph must not interfere with changes in the organ's volume. In every oncograph there are two openings: one for connection with the recording device, and another for the entry of blood vessels, nerves, bronchi, ureters, excretory ducts, etc. These structures should not be compressed, but on the other hand, the device must be hermetically sealed. The interior of the oncograph is filled with some liquid, usually oil. The device records changes in the volume of the organ, which are usually a consequence of changes in the organ's blood filling (sometimes, as for example in the pulmonary oncograph, it is a matter of air filling). With each systole of the heart, acceleration of the arterial blood flow is observed; the oncograph registers these accelerations as rapid pulsatile fluctuations in volume. When the organ's vessels dilate, an increase in movement is recorded; when they constrict, a prolonged change in volume is recorded. The most frequent application of the oncograph is for studying vaso-motor reactions of the organ.