1. The production of multiple emboli of the pulmonary capillaries and arterioles results in rapid and shallow breathing which may be associated with anoxemia, but is not dependent for its occurrence upon anoxemia.
2. Similarly there may occur an increase in the partial pressure of CO2 in the blood as well as an increase in hydrogen ion concentration.
3. These changes must be regarded as the result of the impaired pulmonary function.
4. They are not, however, the cause of the rapid and shallow respirations, since the abnormal type of breathing may occur without the attendant blood changes.
5. The characteristic type of response to increase in CO2 tension is an increased rather than a decreased depth of respiration.