COMPARATIVE HISTOLOGY AND PHYSIOLOGY OF THE SPLEEN. 295 



(12) Cells apparently homologous with the giant cells of the mammalian spleen were 

 found in the spleen of the tortoise. 



(13) They seem to be a concomitant of the blood-forming activity of the spleen ; 

 they are associated with numerous erythroblasts and nucleated red cells in the pulp, 

 and frequently with active karyokinesis in the follicles. 



(14) They multiply usually by karyokinesis, but they probably divide sometimes 

 by simple fission. 



(15) They have usually a large central nuclear heap that gives ofTpyriform buds. 



(16) The nuclear buds, when isolated in the cell, resemble the nuclei of nucleated red 

 blood-corpuscles or of erythroblasts ; while near the middle of the giant cell they are 

 somewhat small, stain deeply, and resemble the nuclei of the nucleated red blood- 

 corpuscles : when near the periphery of the cell they are larger, they stain faintly 

 (they thus resemble the nuclei of erythroblasts), and may be surrounded by a special 

 covering of hyaline protoplasm. 



(17) The greater part of the protoplasm of the giant cells is coarsely granular, but 

 there is a more or less narrow hyaline rim which has a faint but distinct yellow colour 

 like that of the perinuclear protoplasm of the erythroblasts, and similar to, only not so 

 deep as that of the red blood-corpuscles. 



(18) The giant cells usually possess vacuoles that appear to mark the former position 

 of detached nuclear buds. 



(19) The vacuoles situated near the periphery of the giant cell sometimes contain 

 erythroblasts. 



(20) The ruptured vacuoles on the surface of the giant cells have the character of 

 mouth-like openings, and in them erythroblasts are frequently lodged. 



(21) The giant cells probably never contain non-nucleated red blood-corpuscles. 



(22) The giant cells often enter the splenic vein along with the proper corpuscular 

 elements of the blood. 



(23) They occur in the follicles, and some apparently pass into the pulp from the 

 follicles. 



(24) In the pulp they are often contained in cell spaces formed apparently by 

 connective tissue strands, and it is possible that these cell spaces persist, after the 

 disappearance of the giant cells, as the blood spaces of the pulp. 



(25) It is probable that the giant cells are not phagocytes, but that they are 

 producers of erythroblasts. 



(26) The special multinucleated vacuolated cells were found in the spleen of an 

 eight months' human foetus. 



(27) They are apparently derived from giant cells whose nuclei have become 

 isolated, and inclosed each in a vacuole or capsule-like nuclear space. 



(28) In the larger cells a few of the superficial vacuoles alone are empty; in the 

 smaller a few only of the vacuoles contain nuclei. 



(29) After all the nuclei except one or two have disappeared from the vacuoles 



