DEVELOPMENT AND FUNCTION OF HEMAL NODES 387 



time of their appearance* it so happened that the youngest stages 

 were not found in the youngest foetuses as the legends for the 

 accompanying illustrations will show. 



In their earliest stages the subcutaneous hemal nodes of 

 bo\ines are represented merely by condensation,s in the sub- 

 cutaneous mesenchyme. These condensations are syncytial for 

 cell boundai'ies only appear later. It is true that small islands 

 of distinct cells such as those shown in figures 1 to 3 are found 

 in tissue from very young foetuses but these are so numerous 

 that I seriously doubt whether they represent early stages in 

 the development of hemal nodes. Some of them as the one 

 show^n in figure 2, apparently are blood islands rather than cen- 

 ters of foi-mation for hemal nodes. Others such as that shown 

 in figure 3 are the earliest anlagen of the fat lobules one of which 

 in a somewhat later stage of development was found to con- 

 tain a giant cell (fig. 4). 



A less misleading though not uncommon appearance is the 

 presence of a rather large mass of lymphocytes in a well-developed 

 fat lobule as shown in figure 5. In this particular case the mass 

 of lymphocytes is penetrated by a capillary and it is easy to 

 see how these accumulations could suggest the formation of 

 l}aiiph and hemal nodes both in and from fat. Regarding the 

 exact nature of still other accumulations like those shown in 

 figures 6, 7 and 8 I am still in doubt. These accumulations of 

 lymphocytes about capillaries and arterioles are never encap- 

 sulated, are not at all well circumscribed and may be cylindrical 

 in form. From my observations on supernumerary spleens 

 I would be willing to believe that a hemal node might arise also 

 in this way. Indeed, it requires no stretch of the imagination 

 or violation of morphogenic conceptions to consider figure 7 

 and 8 as a representation of early hemal nodes. All that is neces- 

 sary is the assumption that chronological ^'ariations in the 

 vascularization of the early anlagen occur. For such an as- 

 sumption there is abundant evidence in the whole morphology 

 of hemal nodes. Nevertheless I would not consider such a 

 genesis as the normal or usual one and prefer not to urge it 

 especially since such accumulations are relatively coinmon. 



