PHYSIOLOGICAL 283 



arteries, which bear the impure blood from the right ventricle to 

 the lungs. 



THE SPLEEN.— It is difficult to believe that Aristotle, surely 

 one of the best brained of men, did not know what the brain is 

 for. Yet he seems to have been so far from the error of a later 

 disciple, who said that the brain secretes thought as the liver does 

 bile, that he speaks of the brain secreting mucus! The fact is that 

 Aristotle thought of what we call the functions of the brain as 

 having their seat in the heart. 



It is much easier to understand the long-continued obscurity in 

 regard to the spleen, for its functions are intricate and elusive, not 

 indicated like those of the brain by the associated nerves, or like 

 those of the heart by the associated blood-vessels. It is only in 

 recent years that it has become possible to speak with much 

 definiteness regarding the r61e of the spleen, and even now the 

 doctors differ. All are agreed, however, that their predecessors 

 were wrong; and there is no doubt that we must entirely dismiss 

 the libel that the spleen has to do with bad temper. We read in 

 old books that the judge was suffering from a bad attack of the 

 spleen, and consequently pronounced very severe sentences. Or, 

 again, we read that the irascible master vented his spleen on his 

 servants. No doubt a disturbance in any organ may be correlated 

 with irritability of temper, but there is no particular warrant for 

 blaming the spleen. Indeed, it is more innocent of offence than many 

 another structure. 



In most backboned organisms, from skate to man, the spleen 

 is a deep red body situated to the left of the stomach. It is a some- 

 what spongy organ, for it is traversed by a network, partly muscular, 

 in the meshes of which there is a pulp consisting of various kinds 

 of cells. The muscular tissue is of the unstriped or slowly contract- 

 ing type, and its ceaseless contractions and relaxations help to 

 keep up an ebb and flow of blood in the spleen. Thus we might 

 almost think of the spleen as a minor and accessory heart, all the 

 more since it is a reservoir for red blood corpuscles. The rhythmical 

 compressions and dilatations of the spleen, brought about by 

 contractions and expansions of its muscular tissue, take place 

 about once a minute, and are under the control of nerves from the 

 spinal cord and from the S5mipathetic nervous system. But these 

 big waves are made up of smaller waves, and these of smaller 

 wavelets still, corresponding respectively to the breathing move- 

 ments and the heart-beats. But the activity of a skate's spleen is 

 apparently much less intense than that of a mammal. 



An interesting feature is that while the arteries and veins of 

 the body must be thought of as forming a closed system, the ends 

 of the arteries being connected by capillaries to the beginnings of 



