SPLEEN. 451 



sugar. We have already, iu discussing the formation of glycogen, called 

 attention to the fact that in severe cases of diabetes the sugar must have a 

 non-amylaceous source ; and the fact that the urea is increased (and that 

 too in some cases in ratio with the sugar) in diabetes, suggests that the 

 sugar may arise from proteids which have been split up into a nitrogenous 

 (urea) and a non-nitrogenous moiety, and so points out the way in which 

 proteids may be a source of glycogen. 



As a sort of converse to diabetes we may mention that the administra- 

 tion of arsenic in sufficient doses or for an adequate time prevents an accu- 

 mulation of glycogen in the liver and apparently in the body generally, 

 whatever be the diet used. The presence of the metal in the hepatic cell 

 seems to prevent the cell substance from manufacturing glycogen either 

 from carbohydrate material brought to it, or out of its own substance. As 

 another kind of converse we may also state that the administration of 

 glycerin, especially through the alimentary canal, diminishes the effect of 

 the diabetic puncture, or of morphia or of other poisoning, in hurrying on 

 the hepatic store of glycogen into sugar, and thus diminishes the sugar in 

 the urine; the presence of the glycerin in the hepatic cell appears to be in 

 some way a hindrance to the conversion of the glycogen into sugar. Now 

 glycerin injected into the alimentary canal of a normal animal leads to an 

 increase of glycogen in the liver; and the view very naturally suggests 

 itself that this increase arising from the glycerin is to be explained by the 

 glycerin inhibiting in some way a normal conversion of the glycogen store 

 into sugar which is continually going on, and thus increasing for the time 

 that store. 



SPLEEN. 



389. The movements of the spleen. After a meal the spleen increases 

 in size, reaching its maximum about five hours after the taking of food ; it 

 remains swollen for some time, and then returns to its normal bulk. In 

 certain diseases, such as the pyrexia attendant on certain fevers or inflam- 

 mations, and more especially in ague, a somewhat similar temporary enlarge- 

 ment takes place. In prolonged ague a permanent hypertrophy of the 

 spleen, the so-called ague-cake, occurs. 



The turgesceuce of the spleen seems to be due to a relaxation both of the 

 small arteries and of the muscular tissue of the capsule and of the trabeculse ; 

 to be, in fact, a vascular dilatation accompanied by a local inhibition of the 

 tonic contraction of the other plain muscular fibres entering into the struc- 

 ture of the organ, the latter, at all events in some animals, being probably 

 the more important of the two. And the condition of the spleen, like that 

 of other vascular areas, appears to be regulated by the central nervous sys- 

 tem, the digestive turgescence being fairly comparable to the flushed con- 

 dition of the pancreas and of the gastric membrane during their phases of 

 activity. 



The application of the plethysmographic method to the spleen, carried 

 out in the way which we described in speaking of the kidney ( 346), 

 enables us to study more exactly the variations in volume which the organ 

 undergoes. 



A "spleen curve" (Fig. 117) taken in the same way as a " kidney curve" 

 does not, in the dog at all events, show variations in the volume of the spleen 

 corresponding with the pulse waves. The kidney curve, as we have seen, 

 ( 346), gives clear indications of each heart-beat, but the spleen curve 

 shows, besides the larger waves of which we shall speak directly, only undu- 

 lations due to the respiratory movements ; and these, always very slight, are 



