VAKIATIONS IN THE VOLUME OF THE SPLEEN. 417 



constitution very fully. Cholesterine has been found to exist in the spleen 

 constantly and in considerable quantity, and the same may be said of uric 

 acid. In addition, chemists have extracted from the substance of the spleen, 

 hypoxanthine, leucine, tyrosine, a peculiar crystallizable substance called, by 

 Scherer, lienine, crystals of haematoidine, lactic acid, acetic acid, butyric acid, 

 inosite, amyloid matter and some indefinite fatty matters. 



Variations in the Volume of the Spleen. One of the theories with regard 

 to the uses of the spleen, which merits some consideration, is that it serves 

 as a diver tic ulum for the blood when there is a tendency to congestion of the 

 other abdominal viscera. 



It has been shown that the spleen is greatly enlarged in dogs four or five 

 hours after feeding, that its enlargement is at its maximum at about the fifth 

 hour, and that it gradually diminishes to its original size during the succeed- 

 ing twelve hours ; but it is not apparent how far these changes are important 

 or essential to normal digestion and absorption. Experiments have shown 

 that animals may live, digest, and absorb alimentary matters after the spleen 

 has been removed, and this has been observed even in the human subject. 

 In view of these facts, it can not be assumed that the office of the spleen, 

 as a diverticulum for the blood, is essential to the proper action of the other 

 abdominal organs. 



Changes in the volume of the spleen may be produced by operating on 

 the nervous system, chiefly through the vaso-motor nerves. Section of the 

 nerves at the hilum increases the size of the spleen by increasing the quantity 

 of blood which it receives ; and stimulation of these nerves produces contrac- 

 tion of the spleen. It is stated that stimulation of the medulla oblongata 

 diminishes the size of the spleen, and that the same result can be produced 

 by reflex action, stimulating the central ends of the pneumogastrics or of 

 various sensory nerves, provided that the splanchnic nerves be intact. Start- 

 ing from the medulla oblongata, the nerve-fibres which influence the size of 

 the spleen pass down the spinal cord to the lower dorsal region, enter the 

 semilunar ganglion by the left splanchnic, and are distributed to the spleen 

 through the splenic plexus. 



Extirpation of the Spleen. There is one experimental fact that has pre- 

 sented itself in opposition to nearly every theory advanced with regard to 

 the uses of the spleen, which is that the organ may be removed from a liv- 

 ing animal and yet all the processes of life go on apparently as before. The 

 spleen is certainly not necessary to life, nor, as far as is known, is it essential 

 to any of the important general functions. It has been removed from dogs, 

 cats, and even from the human subject, and its absence is attended with no 

 constant and definite changes in the phenomena of life. If it act as a diver- 

 ticulum, this is not essential to normal digestion and absorption ; and if its 

 office be the destruction or the formation of the blood-corpuscles, the forma- 

 tion of leucocytes, of uric acid, cholesterine or of any excrementitious matter, 

 there are other organs which may perform these acts. Extirpation of the 

 spleen is an old and a very common experiment. In the works of Malpighi, 

 published in 1687, is an account of an experiment on a dog, in which the 



