506 VETERINARY PHYSIOLOGY 



the destruction of erythrocytes is shown by the facts (i) 

 that injections of extracts of the spleen cause no change in 

 the number of corpuscles ; (ii) that removal causes no 

 increase in the number of erythrocytes ; (iii) that, when 

 blood is injected, the added corpuscles are not removed 

 more quickly in the normal than in the spleenless animal. 



2. The spleen is rather to be regarded as a scavenger, 

 which removes dead erythrocytes from the blood. This is 

 indicated by the facts (i) that, after injecting hcemolytics, 

 such as phenylhydrazin, there is less marked anseniia in the 

 spleenless animals on the fourth day, because the dead 

 corpuscles are not removed from the blood ; (ii) that the 

 remains of the corpuscles may be seen in the cells of the 

 spleen, and chiefly in the endothelial cells of the sinuses ; 

 (iii) that iron compounds from the hemoglobin accumulate 

 in the spleen after haemolysis. A result of this is that if 

 rabbits are fed on a food poor in iron such as rice they 

 become anaemic more rapidly if the spleen has been removed, 

 because they have a smaller store of iron to draw upon. 



C. Digestion. — It has been suggested that the spleen 

 manufactures a kinase which activates the pancreatic 

 juice, but the evidence is against this theory. 



The spleen probably acts as a blood reservoir regulating 

 the supply of blood to the digestive organs. 



On the purin metabolism it may have an effect (see p. 

 556) ; on the general metabolism it has no action. 



D. Movements. — The visceral muscle in the framework 

 of the spleen undergoes rhythmic contraction and relax- 

 ation, and the organ thus contracts and expands at regular 

 intervals of about a minute. In the dog the movements are 

 very marked. 



These movements may be recorded by enclosing the 

 organ in an oncometer, a closed capsule connected with some 

 form of recording apparatus. They are controlled by nerve 

 fibres, from the true sympathetic system, leaving the spinal 

 cord chiefly in the 6 th, 7 th, and 8th dorsal nerves of both 

 sides. Strong stimulation of these causes contraction, 

 which is also caused by the intravenous injection of 

 adrenalin. 



