200 EXPERIMENTAL PHYSIOLOGY 



established the rate of heart beat is increased and the mean pressure 

 becomes higher. 



The changes of kidney volume do not exactly follow those of the 

 blood pressure, but are to a certain degree independent of them. 

 After a period of delay, which is longer than that necessary to produce 

 changes in the blood pressure, there is a sudden constriction of the 

 kidney vessels, at first very rapid, then more gradual, and finally 

 so marked that the variations due to heart beat are almost obliterated. 

 In this part of the trace a dilatation is to be observed synchronous 

 with the rise of pressure due to the inspiratory spasms. Next follows 

 a very sudden dilatation, and the volume then follows the blood- 

 pressure changes very closely until respiration recommences, when a 

 further very marked dilatation takes place, the volume becomes greater 

 than initially, and then as respiration and blood pressure gradually 

 return to the normal, so the kidney volume recovers, thougn at a 

 slower rate than the blood-pressure changes. During the marked 

 second dilatation the rate of urinary flow is increased. 



THE COURSE OF THE VASO-MOTOR NERVES TO 

 THE KIDNEY 



By means of oncometer experiments the vaso-motor nerves to the 

 kidney have been mapped out. Vaso-constrictor nerves are proved to be 

 present among the particular fibres stimulated if a diminution of the 

 kidney volume result, accompanied by either no change or by a rise 

 of blood pressure. Simultaneous records of the blood pressure 

 changes exclude the possibility of the observed kidney changes 

 being due to variations brought about passively on changes in the 

 blood pressure. These nerves have thus been proved for the dog to 

 leave the cord mainly in the anterior roots of the 11th, 12th, and 

 13th thoracic nerves, and to a less extent in the 7th, 8th, and 9th. 

 Nerve cells, shown by the nicotine method (see p. 133), are found on 

 the course of these fibres, situated in the cceliac, mesenteric, or renal 

 ganglia. Vaso-dilators have been found in the 11th, 12th, and 13th 

 anterior roots with ganglion cells in the solar or. renal ganglia. 



