740 MOVEMENTS OF THE SPLEEN. [BOOK n. 



exhibit amoeboid movements, and are often irregular in form, 

 are characterized by the presence in their cell-substance of 

 red corpuscles, sometimes in almost a natural condition, some- 

 times more or less irregular in shape with their red haemoglobin 

 changing into the browner hsematin, and sometimes disintegrated 

 into a mass of brown granules. The fluid or plasma in which 

 these cells float also contains besides normal red corpuscles a 

 certain number of red corpuscles in various stages of change, as 

 well as pigment granules which appear to be derived from 

 haemoglobin. Obviously a certain number of red corpuscles do 

 undergo change in the* spleen, but whether the change is mainly 

 effected in the cell-substance of the celts just mentioned, or takes 

 place in the plasma, the products of disintegration being sub- 

 sequently taken up, in amoeboid fashion, by the cells in question is 

 not as yet clear. Besides the above, in the spleen of young 

 animals, nucleated cells with haemoglobin holding cell-substance, 

 haematoblasts (see 27), have been described; these are said to 

 appear also in the spleen of adults after very great loss of blood. 



475. The Movements of the Spleen. As we have already 

 stated, the volume of the spleen is subject to considerable variations. 



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 in the pyrexia attendant on certain fevers or 

 inflammations, and more especially in ague, a somewhat similar 

 temporary enlargement takes place. In prolonged ague a per- 

 manent hypertrophy of the spleen, the so-called ague-cake, occurs. 



The turgescence 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 trabeculae ; to be, in fact, a vascular dilation accom- 

 panied by a local inhibition of the tonic contraction of the other 

 plain muscular fibres entering into the structure 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 system, the digestive turgescence being fairly comparable 

 to the flushed condition 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 ( 410), enables us to study more exactly the variations in 

 volume which the organ undergoes. 



A ' spleen curve ' (Fig. 95) taken in the same way as a ' kidney 

 curve' does not, in the dog at all events, shew variations in the 

 volume of the spleen corresponding with the pulse waves. The 

 kidney curve, as we have seen ( 410), gives clear indications 

 of each heart-beat, but the spleen curve shews, besides the larger 

 waves of which we shall speak directly, only undulations due to the 



