380 ARTHUR WILLIAM MEYER 



l}iiij)li iiodey in the region of the neck and of the thoracic aorta 

 of the pig "parallels the stages in the development of the other 

 (lymph) nodes, except that its sinuses from the beginning be- 

 long to the bloodvessels rather than the l>^nph vessels. In 

 Ijanphatic nodes the sinuses are made of modified veins, Cialled 

 l^anphatics, while in the hemolymph nodes they ar-e made of 

 the veins themselves .... The hemolymph node found 

 in the neck of the pig is from the beginning a distinct 

 organ, different in type from the lymphatic node." According 

 to Sabin ''The hemolymph node does not occur in the neck of 

 the pig until the embryo is about 23 cm. long." This conclu- 

 sion of Sabin also agrees with my own observ^ations on bovine 

 fetuses. The superficial lymph nodes of these fetuses are well 

 developed before the subcutaneous hemal nodes make their ap- 

 pearance. I also found the superficial lymph nodes well formed 

 before the subcutaneous fat appears. This fat usually occurs 

 in fetuses about 21 cms. long. Engel '09-' 10 also emphasized 

 the fact that it can be seen even macroscopically, that there is 

 no developmental connection between the cervical fat and the 

 cervical lymph nodes. Engel found the latter present in their 

 characteristic locations before the fat appeared. 



In an article on "The lymphatics" Sabin '07 further pictured 

 a developing 'haemal' node from the neck of a foetal pig^ 24.5 

 cm. long and stated that the haemolymph or haemal nodes of 

 man are either red or brown in color according to their state 

 of functional activity. They are brown when they contain 

 pigment and red when they contain erythrocytes. 



In 1911-12 Sabin stated that "Haemal glands have not been 

 found in human embryos," and that in the earliest stage in 

 the pig "the gland consists of a single follicle around a plexus 

 of blood capillaries and surrounded by a sinus of bloodvessels 



A group of lymph follicles makes a lymph gland ; 



a group of blood follicles makes a hemal node." 



2 The results obtained recently in numerous puncture injections on absolutely 

 fresh carcasses of young and adult pigs leave me without any evidence for the 

 presence of hemal nodes in the pig. Reddened lymph nodes are practically 

 constant. 



