490 SOLITARY FOLLICLES. [BOOK n. 



contains leucocytes ; but in the follicle the network is finer, closer 

 and more regular than elsewhere, the meshes are almost com- 

 pletely filled with leucocytes, and the spherical mass breaking 

 through the muscularis mucosae reaches some way down into the 

 submucous tissue. Over the surface of the follicle, which bulges 

 somewhat into*) the interior of the intestine, villi may be present, 

 but the glands of Lieberkiihn are pushed aside and are found only 

 at its circumference. Into this mass of adenoid tissue one or 

 more small arteries enter and break up into a capillary network 

 the blood from which is carried away by one or more small veins. 

 Around the mass there is placed a more or less well developed 

 spherical lymph space, lined with sinuous epithelioid plates and 

 continuous with the neighbouring lymphatic vessels. This lymph 

 space or lymph-sinus as it is called thus forms a hollow jacket 

 filled with lymph round the spherical mass of adenoid tissue, but is 

 not complete, being broken by the entering and issuing blood 

 vessels, or by imperfect partitions passing from the tissue without 

 to the adenoid tissue within. The blood vessels and bridles in 

 question are covered by a layer of epithelioid plates continuous 

 with that lining the outer wall of the jacket, as also with the one 

 which more or less completely invests the inner mass of adenoid 

 tissue. 



The leucocytes which occupy the meshes are of different sizes. 

 Some are as large or almost as large as white blood-corpuscles, 

 from which indeed they chiefly differ in the fact that their nuclei 

 exhibit a nuclear network which as we have seen ( 28) is 

 apparently not present in the white corpuscle of the blood. The 

 majority however are much smaller than white blood corpuscles, 

 their smallness being chiefly due to the small amount of cell- 

 substance surrounding the nucleus ; in some only a mere film of 

 cell-substance can be detected so that the nucleus appears almost 

 as a so-called ' free ' nucleus. Many of the leucocytes may be seen 

 to be undergoing karyomitosis, indicating that they are multi- 

 plying by division; and indeed there are many reasons for 

 thinking that in the adenoid tissue of these follicles and other 

 similar structures a very considerable multiplication of leucocytes 

 takes place. Many of the leucocytes of these follicles exhibit 

 under favourable circumstances amoeboid movements, and the 

 smaller leucocytes, indeed even the smallest, seem at times as 

 active as the larger ones. 



A solitary follicle then may be considered as consisting in 

 the first place of a rounded capillary network fed and drained by 

 small arteries and veins, all supported by a minimal amount of 

 ordinary connective tissue. In the second place the interstices 

 of this vascular network are filled up with adenoid tissue the fine 

 meshes of which are crowded with leucocytes of variable but on 

 the whole small size. Lastly the rounded mass thus constituted 

 is surrounded by a lymph sinus, the fluid of which on the one hand 



