308 PHYSIOLOGY. 



In surgical shock and in collapse we have a low pressure, blood 

 pools in the most dependent parts or in the splanchnic area. The 

 splanchnic arterioles regulate the variations of systemic blood-pressure, 

 and they have been called the "resistance box" of the circulation. 

 There is an antagonistic play between the splanchnic system and 

 cutaneous circulation. When one contracts the other dilates, which 

 explains the cold feet or chilliness during digestion. Stolnikow has 

 shown that the liver also acts as a blood reservoir for the systemic 

 circulation, whilst the lungs act as a reservoir for the pulmonary 

 circulation. Hence we have pooling of the blood in the vessels of the 

 liver and lungs in a weak heart. In the lax abdominal muscles of 

 women or in weak vasomotor centers, the blood can pool in the splanch- 

 nic area when standing for a long time and cause fainting. In neuras- 

 thenia the vasomotor system loses local control and we have throbbings 

 and flashes of heat. 



In unconsciousness produced by chloroform the blood-pressure 



Fig. 103. Traube-Hering Curves. (FREDERICQUE.) 



falls about 30 millimeters. Alcohol depresses arterial tension. 

 Faivre, by actual measurement in man during the amputation of a 

 leg, found the mean pressure 115 millimeters. 



Respiratory Undulations. In studying a graphic record of the 

 heart's action one is struck with the almost rhythmical rise and fall 

 of the general tracing. There is thus depicted the condition of arte- 

 rial pressure conjointly with the graphic representation of the heart- 

 beats. They are produced by the respiratory movements, and hence 

 have been termed respiratory undulations. 



Traube-Hering Curves. These are curves which are higher than 

 the regular respiratory undulations, but less frequent. They are due 

 to alterations in the condition of the small arteries, superinduced 

 by the waxing and waning at regular intervals of the excitability of 

 the main vasomotor center. 



Vagus and Blood-pressure. When the blood-pressure rises in an 

 animal the usual sequence is for the pulse-rate to be diminished by 

 virtue of stimulation to the cardio-inhibitory center of the vagus. A 

 fall in the blood-pressure is followed by an increase in the rate of 



