CH. XXIII.] 



THE SPLEEN. 



327 



(i) stimulation of the spinal cord; (2) reflexly by stimulation of 

 the central stumps of certain divided nerves, e.g., vagus and sciatic ; 

 (3) by local stimulation by an electric current ; (4) by the adminis- 

 tration of quinine and some other drugs. 



It has been shown by the oncometer of Roy that the spleen 

 undergoes rhythmical contractions and dilatations, due to the 

 contraction and relaxation of the muscular tissue in its capsule 

 and trabeculse. A tracing also shows waves due to the rhythmical 

 alterations of the general blood-pressure. 



The form of oncometer adapted for the shape of the spleen 



SECONDS 

 nnfnnnrvTrYTirryirrrrvTrrrrrrrrmTrrr^ 



Fig. 300. The upper tracing is the spleen record ; the next is carotid blood pressure taken 

 with a mercurial kymograph. The straight line beneath this is the abscissa of the 

 arterial pressure ; and the lowest tracing is the time in seconds. 



of most animals is shown on p. 326. In most mammals the 

 spleen is not kidney-shaped as in man, but narrow and ribbon 

 shaped. The general principles of the oucometer have been 

 explained on p. 309, where it is mentioned that by an air onco- 

 meter Schafer has obtained good tracings ; these show first, the 

 large waves occurring about once a minute, due to the splenic 

 systole and diastole ; secondly, smaller waves on this, due to the 

 effect of respiration on the blood-pressure ; and on these, smaller 

 waves still, corresponding with the individual heart-beats. The 

 large waves due to the splenic contractility still go on after 

 the division of all the splenic nerves. These nerve-fibres leave 

 the spinal cord in numerous thoracic anterior roots ; they have 



