742 MOVEMENTS OF THE SPLEEN. [BOOK n. 



these animals may be considered as a muscular organ, now ex- 

 panding to receive a larger quantity of blood and now contracting 

 to drive the blood on to the liver. When the muscular elements 

 are scanty in or absent from the capsule and trabeculae, the 

 expansion and contraction of the whole organ must depend alone 

 or chiefly on variations in the width of the supplying arteries. 

 We have evidence moreover that the muscular activity of the 

 spleen, whether of the muscular capsule and trabeculse and arteries 

 combined or of the latter alone, is under the dominion of the 

 nervous system. A rapid contraction of the spleen may be brought 

 about in a direct manner by stimulation of the splanchnic or 

 vagus nerves, or in a reflex manner by stimulation of the central 

 end of a sensory nerve ; it may also be caused by stimulation 

 of the medulla oblongata with a galvanic current or by means 

 of asphyxia. Though the matter has not yet been fully worked 

 out, we have already sufficiently clear indications that the flow 

 of blood through the spleen is, through the agency of the nervous 

 system, varied to meet changing needs. At one time a small 

 quantity of blood is passing through or is being held by the 

 organ, and the metabolic changes which it undergoes in the 

 transit are comparatively slight. At another time a larger 

 quantity of blood enters the organ, and is let loose, so to speak, 

 into the splenic pulp, there to undergo more profound changes, 

 and afterwards to be ejected by the rhythmic contractions of the 

 muscular trabeculae. 



It is further obvious that these changes going on in the spleen 

 must have an important influence on the changes going on in the 

 liver ; it cannot be of indifference to the latter organ whether a 

 relatively small quantity of blood, relatively little changed, reaches 

 it from the spleen, or whether it receives a relatively large quantity 

 of blood, profoundly altered by the changes which it has undergone 

 in the spleen pulp. 



476. The Chemical Constituents of the Spleen. Besides the 

 chemical bodies which one would expect to find in a vascular, 

 muscular organ full of blood, the spleen contains bodies, lodged 

 apparently in the spleen pulp, which give it special chemical 

 characters. One of the most important of these is a special proteid 

 of the nature of alkali-albumin, holding iron in some way peculiarly 

 associated with it. The occurrence of this ferruginous proteid, 

 accompanied as it is by several peculiar but at present little 

 understood pigments, rich in carbon, which are partly present in 

 the cells spoken of above and partly deposited in the branched 

 cells of the reticulum, appears to be connected with the changes 

 undergone by the haemoglobin which we shall presently discuss. 

 The inorganic salts of the spleen, or at least those of its ash, are 

 remarkable for the large amount of both soda and phosphates, and 

 the small amount of potash and chlorides which they contain, thus 

 differing from those of blood-corpuscles on the one hand, and from 



