R - ''in. 



studying the formation of the sinuses. The question 

 of • opraent of reticulum hae been taken up by Mall (84). 



rd to the formation of the lymph cords and follicles, the funda- 

 mental point is the question of the origin of the Lymphocytes themselves. 

 This I shall not undertake to discuss. The lymphocytes may 



or diffusely in all of the trabeculse of the developing node and thi6 

 simplest form of a gland. This form is Bhown by Jolly (59) 

 in his plate IX. fig. ;; . for the lumbar glands in birds, by Kling (72), 

 plate X.WII. fig. 11. for the axilla r\ glands in human embryos ami 

 in fig. 9 (Sabin I'M) from the primary jugular lymph glands in 

 the pig. It will be noted thai all of these figures are from primary 

 lymph glands. The definite follicle- may develop in the center or in 

 the periphery of a node, and there is every possible variation in 



proportion of the diffuse cords and the definite follicles. Thi 

 are two processes in the development of the follicle: (1) an increase 

 in the number of lymphoi orming a definite clump, and (2) 



formation of a tuft of blood capillaries. Both the cords and the 

 follicle- form along the blood vessels, the follicles coming at the cap- 

 illary bed. 



A- I have said, the earlj glands which come from the primary sacs 

 pass through the form of diifuse distribution of Ihe lymphocytes. 

 Follicles which develop later, however, ma\ heuin at once a- clumps 

 of lymphocytes, making very definite follicles Burrounded by a lym- 

 phatic plexus. A number of such tiny follicles are to he seen in li.L r . 

 L6 - 131), which is the developing group of inguinal lymph 



glands in a pig 2 1.5 cm. long. 



Lymph glands may he either simple, consisting of one follicle with 

 a peripheral sinus, or compound, with many follicles ami cords, and 

 both peripheral and centra] sinuses. 



The subject of haemolymph glands ha- been taken up by Belly in 

 the Ergebnisse fur Anatomie ami Entwickelungsgeschichte for 1902. 



VII. COMPARATIVE MORPHOLOGY OF THE PRIMARY 

 LAM I'll SACS, LYMPH HEARTS, AMPHIBIAN LYMPH 

 SACS Wl> LYMPH GLANDS. 



We are now in a position to consider the comparative morphology 

 of lymph sacs ami lymph hearts. 1 -hall not attempt to analyze the 

 work of Pavaro (36a) and of Allen (2-4) on lymphatic- m fishes, 



