THE DUCTLESS GLANDS 1195 



It is evident that the blood must meet with considerable resistance in 

 passing through the close mesh work of the splenic pulp. In order to ensure 

 a constant circulation through the gland, the muscular tissue of the capsule 

 and trabeculse has the property of rhythmic contraction. If the spleen be 

 enclosed in a plethysmograph, or splenic oncometer, and its volume be 

 recorded by connecting this with an oncograph, it will be seen to be subject 

 to a series of large, slow variations, each contraction and expansion lasting 

 about a minute, and recurring with great regularity (Fig. 551). Superposed 

 on these large waves are smaller undulations due to the respiratory variations 

 of the blood- pressure, and on these again the little excursions corresponding 

 to each heart- beat. The contractile power of the spleen is under the 

 control of the nervous system, and a rapid contraction may be induced by 

 stimulation of the splanchnic nerves. 



FUNCTIONS OF THE SPLEEN 



The structure of this organ suggests that the splenic cells must exercise 

 a constant influence on the blood which surrounds them, and that this 

 influence is not purely of a chemical nature. In the liver and kidneys, 



FIG. 552. Cells from a scraping of the spleen. (KOLLIKER.) 

 A, splenic pulp-cell containing red blood-corpuscles, b (k = nucleus) ; B, leucocyte 

 with polymorphous nucleus ; c, pulp-cell containing disintegrated red corpuscles ; 

 D, lymphocyte ; E, giant cell ; r, nucleated red corpuscles ; G, normal red corpuscle ; 

 H, multinuclear leucocyte ; j, eosinophile cell. 



which exercise so powerful an effect on the composition of the blood passing 

 through them, the proper cells of the organs are separated from the blood- 

 stream by the capillary wall. Microscopic examination of the cells of the 

 splenic pulp shows us that these are full of particles of brown pigment 

 or fragments of red corpuscles (Fig. 552). In many cases of infectious 

 disease, such as recurrent fever, the splenic cells are observed towards the 

 end of the attack to be full of the organism spirillum which is the cause of 

 the disease. In fact, these cells are so arranged that they can take up solid 

 particles held in suspension in the blood-plasma. We must indeed look 

 upon the spleen as the great blood-filter, purifying the blood in its passage by 



