DEVELOPMENT AND FUNCTION OF HEMAL NODES 377 



never takes place in the subcutaneous hemal nodes of bovines 

 and hence probably also not in case of the hemal nodes of the 

 sheep. It may here be recalled that Drunmiond, '00, stated 

 that ''. . . . at a comparatively early stage in the de- 

 velopment of the l>aii»phatic structures in the embryo, the haemo- 

 l}^nph glands are quite readily distinguishable from ordinary 

 l\^nph glands even to the naked eye." von Schumacher, '12 a, 

 however, declared that he could not distinguish the Anlage of 

 the lymph from that of the hemolymph node. It has been 

 the writer's experience to repeatedly mistake and excise small 

 aberrant adren^als, small hemorrhagic areas, very vascular or 

 injected fat lobules, a small plexus of blood vessels — especially 

 of veins — parathyroids, small deeply pigmented spots in tis- 

 sues, etc., for hemal nodes even in the adult. Indeed, there is 

 at present, no means for identifying these various structures 

 except by microscopical examination and injection. Hence, it 

 is evident that positive gross differentiation between early em- 

 bryonic or developing hemal or lymphatic nodes even with the 

 aid of a hand lens must be wholly unreliable at present of course. 

 Moreover, fully-formed hemal nodes which are so small that 

 they can be excised and transferred satisfactorily only under 

 magnification are frequently found even in adult animals. In 

 the case of these minute specimens positive identification by 

 means of the unaided eye must, to be sure, be wholly out of 

 the question for they are unfortunately entirely too small to 

 permit of direct injections. 



Although Drummond's 'GO article was accompanied by a draw- 

 ing of a hemal node from a sheep foetus he said nothing about 

 the development of these hemal nodes, but described those 

 from a bovine foetus nine inches long. However, Warthin '02 (a 

 and b) stated that the "New formation of hemolymph glands in 

 adipose tissue was observed and the various stages of develop- 

 ment traced. A change of hemolymph glands into ordinary 

 lymph glands was also noted." According to Warthin ''the 

 new formation of these structures repeats their embryonal de- 

 velopment and the earliest stages of development of both forms 

 may run parallel." Moreover, Warthin added ''The latter [the 



