COMPARATIVE HISTOLOGY AND PHYSIOLOGY OF THE SPLEEN. 281 



a little larger than the isolated nuclei of the giant cells ; they measure 7-8 m in diameter, 

 and they stain somewhat less deeply with haematoxylin. They have sometimes a 

 rather wide rim of protoplasm and sometimes two nuclei, while some of the cells 

 lying near the open mouths of vacuoles appear not to have any perinuclear protoplasm. 

 Cells similar to these occur in clumps at frequent intervals throughout the pulp. 



In two spleens of foetal pigs similar giant cells were found, but in them the 

 vacuolation is not so pronounced, and there is less isolation of their nuclei. The 

 latter are sometimes in the form of a convoluted chain, and occasionally numerous 

 pyriform nuclei radiate outwards from the middle of the cell, their apices pointing 

 inwards. The giant cells in the foetal spleen are slightly less numerous than in the 

 spleen of the young pig, and they are also a little larger, their average measurement 

 being 30 fi by 22 //,, as compared with 30 fi by 18 ju,. 



In the adult Ox and Sheep the splenic pulp very closely resembles that in the 

 adult pig, so that one description may serve for the three ungulate animals. 



In the spleen of the Dog the cell processes that form the reticulum are much less 

 expanded than those in the pig, and the whole reticulum is more delicate. 



Giant cells were present in the spleens of five dogs that were examined. In the 

 spleens of three adult dogs they were comparatively few in number, about fifteen in 

 each section ; in the spleen of a half-grown dog they were more numerous, about fifty 

 in a section ; and in the spleen of a puppy they occurred in large numbers, on a rough 

 estimate, about a thousand in each section. 



In the spleen of the adult Dog they were mainly situated in the neighbourhood 

 of the follicles. In one spleen a comparatively small giant cell with four or five nuclei 

 was separated from the artery of the follicle merely by two rows of lymphoid cells, 

 and a similar giant cell, with eight or nine nuclei, was placed just outside the same 

 follicle. In another adult spleen giant cells occur in groups about the middle of the 

 follicles, and others are in the pulp immediately surrounding them. At the periphery 

 of one follicle there was found a giant cell only partly in the pulp : it measured 28 /a 

 by 16 ju,. In another follicle there were seen six or seven somewhat large giant cells, 

 the largest of which (measuring 30 ft by 14 /x) had a single, large, round nucleus (about 

 13 ii in diameter), while in the adjoining pulp there was a multinucleated giant cell, 

 and in a neighbouring venous sinus a mass of protoplasm similar to that of the giant 

 cell, but apparently non-nucleated. This spleen was obtained from an ill-nourished 

 and probably slightly anaemic dog. 



In the spleen of the half-grown Dog some of the giant cells had vacuoles in their 

 substance and also mouth-like openings on their surface. The nuclei of the giant 

 cells showed great diversity of arrangement. Frequently seven or eight faintly stained 

 nuclei were packed together near the middle of the cell in the form of a sphere. 

 Sometimes a cell had three or four large, round nuclei, the cell protoplasm showing 

 indication of division corresponding with each nucleus. The most common appearance 

 was a number of oval nuclei arranged near the middle of the cell close to, but not 



