DEVELOPMENT AND FUNCTION OF HEMAL NODES 397 



aiul the ;i(hent of gijiiit cells is seen. The lymphocytes are 

 acciinuilated at the periphery and mingle freely with the blood 

 in the peripheral blood space which seems to possess no definite 

 boundary. 



Older stages than those here represented are easily obtain- 

 able. Some of these show complete or almost complete develop- 

 ment on one end an,d but slightly differentiated mesenchyme 

 at the other. They suggest that cavernisation and capsule 

 formation may be limited to but a portion of a node for a con- 

 siderable period of time. The fact that the subcapsular spaces 

 are frequently completely empty of erythrocytes also indicates 

 that the vascular conditions within the node but not necessarily 

 the ^'ascular relations of the latter, ^^ary quite markedly in the 

 early developmental stages as well as later on. 



The earliest vascular relations apparently come about through 

 the advent of capillaries which reach the node from the adjacent 

 tissues. The presence of erythrocytes only within the subcap- 

 sular space in some nodes, implies no doubt that capillaries 

 may come into relation with this space first. Such a relation 

 is shown in figure 14, taken from the same node. Here the 

 vascular relations are beyond doubt although 1 am convinced 

 that this direct relationship between the subcapsular blood 

 space and the vascular circulation — except rarely through small 

 confluent veins as reported elsewhere and in wholly depleted 

 nodes — does not exist as a rule in the mature node. 



Some of these foetal nodes lay partly imbedded in the under- 

 lying musculature but a definite capsule and sometime also 

 the fascia, intervened. Not infrequently hemal nodes which 

 were included in the block of tissue removed from the region 

 of the flank lay near lymph nodes but never in them. In serial 

 sections the presence of a lymphatic plexus or of lymphatic con- 

 nections of the Ijrmph nodes could usually be easily ascertained, 

 however. Besides the lymph nodes were generally much larger; 

 especially the main ones. This is undoubtedly due to the fact 

 that they develop much earlier, long before the subcutaneous 

 fat lobules. Some hemal nodes develop much earlier, however, 

 and others undoubtedly later. But in spite of these facts and 



