CHAP, iv.] METABOLIC PROCESSES OF THE BODY. 777 



of other vascular areas, appears to be regulated by the central 

 nervous system, the digestive turgescence being fairly comparable 

 to the flushed condition of the pancreas and of the gastric 

 membrane during their phases of activity. 



The application of the plethysmographic method to the spleen, 

 carried out in the way which we described in speaking of the 

 kidney ( 410), enables us to study more exactly the variations in 

 volume which the organ undergoes. 



A ' spleen curve ' (Fig. 95) taken in the same way as a ' kidney 

 curve' does not, in the dog at all events, shew variations in the 



FIG. 95. NOBMAL SPLEEN CUEVE FBOM DOG. (KoY.) 



The upper curve is the spleen curve shewing the rhythmic contractions and 

 expansions ; the smaller waves are due to the respiratory movements. The lower 

 curve is the blood-pressure curve, and the point a of the spleen curve corresponds 

 in time to the point b of the blood-pressure curve. The marks on the time curve 

 below indicate seconds. 



volume of the spleen corresponding with the pulse waves. The 

 kidney curve, as we have seen ( 410), gives clear indications 

 of each heart-beat, but the spleen curve shews, besides the larger 

 waves of which we shall speak directly, only undulations due to the 

 respiratory movements ; and these, always very slight, are some- 

 times not visible. In the kidney the united volume of the pulsating 

 arteries is so large a part of the volume of the whole organ, that 

 the changes in the former due to the pulse are manifest in the 

 curve of the latter ; in the spleen this is not so. Moreover when 

 the supply of blood to the spleen is wholly and suddenly cut 

 off, as by clamping the aorta, the spleen curve sinks very slowly, 

 shewing that the spleen is diminishing in volume not suddenly 

 but very slowly. 'The pathway of the blood through the splenic 

 reticulum is peculiar ; and increase or decrease in the volume 

 of the spleen means more or less blood held in the spleen 

 pulp, not necessarily a greater or less flow of blood through 

 the organ. 



F. II. 



50 



