FUNCTIONAL MECHANISM OF THE SPLEEN. 391 



to sustain the continuous functional work of the lobular and cor- 

 puscular (Malpighian) elements (destruction of erythrocytes, for- 

 mation of lymphocytes, formation of secretion, etc.) pending the 

 active stage. 



When, as a result of reflex stimuli through the efferent gastro- 

 duodenal branches of the vagus, the spleen becomes functionally 

 active, the vagus impulses impose their rhythm upon the extrinsic 

 motor plexuses (extensions of the splenic plexus), and the vagus 

 system assumes control of splenic functions. As a result, 



(a) The extrinsic arteries are constricted beyond their normal 

 tonic caliber; the speed of the blood-flow into the organ is increased 

 and the blood allowed to slowly accumulate therein (probably owing 

 to restricted caliber of the venous exit), thus causing its dilation. 



(b) About the fourth hour of the digestive process the arterial 

 and venous calibers are equalized and the splenic products (secre- 

 tion, leucocytes, brolcen-down corpuscles, and pigments) are voided 

 into the splenic vein and increased rapidly. This continues for 

 two to four hours, when the calibers are readjusted by the vagus 

 and the organ resumes the passive state. 



An incidental remark of Professor Mall's, in the contri- 

 bution previously referred to, goes far toward demonstrating 

 that we have not erred so far in ascribing to the blood-plasma 

 per se the active part in the blood's function. This constitutes 

 such a far-reaching feature of this entire work that the follow- 

 ing lines appear to us as timely: "The microscopical anatomy 

 shows that the ampullae and venous plexus have very porous 

 walls which permit fluids to pass through with great ease and 

 granules only with difficulty. In life the plasma constantly 

 flows through the intercellular spaces of the pulp-cords, while 

 the blood-corpuscles keep within fixed channels. Numerous phys- 

 iological experiments which I have made corroborate this 

 view." If this can occur in the spleen it is doubtless possible 

 elsewhere in the organism, especially when we consider that 

 red corpuscles average in diameter about 1 / 300 o f an inch, 

 while the lumen of the majority of functional capillaries is less 

 than one-half that size. Of course, corpuscles adjust them- 

 selves to the dimensions of the structures surrounding them; 

 but it is apparent that in many instances the tortuous capil- 

 laries of pericellular net-works, for instance such a system 



