COMPARATIVE HISTOLOGY AND PHYSIOLOGY OF THE SPLEEN. 309 



a post-mortem change. We think it likely that the latter appearances are due to 

 similar causes to those which produce a pigmented zone under the capsule of any 

 spleen that is exposed to the drying influence of the air before hardening. 



In the Bone-Marrow of the femur there are fairly large numbers of giant cells, 

 perhaps about 120 in a section. But they are by no means so close together as in the 

 spleens of some young Mammals, nor in the spleen of the adult hedgehog. Their average 

 size, too, seems to be rather smaller : one of the largest measured 34 by 20 /*, while the 

 average diameter seems to be about 20 /*. Their characters are apparently identical with 

 those of the cells found in the spleen. There are many small giant cells present whose 

 protoplasm stains faintly blue with haematoxylin. Erythroblasts and nucleated red 

 cells occur in large number ; their perinuclear protoplasm has a distinctly yellow 

 tinge ; their nuclei occasionally show karyokinetic figures, — the nuclei at any rate of 

 the erythroblasts, — as do also the nuclei of the giant cells. There are numerous 

 eosinophilous cells present. 



In a Lymphatic Gland taken from the neck there are apparently no giant cells, but 

 there are a few erythroblasts and nucleated red cells, and eosinophilous cells, and fairly 

 numerous pigment cells and coarsely granular protoplasmic corpuscles, all contained in 

 the medullary sinuses of the gland. 



In a Mesenteric Lymph Gland there are a few somewhat small giant cells, whose 

 average diameter is about 20 j<*. Their protoplasm is rather finely granular, and stains 

 only faintly pink with eosine. The nuclei are sometimes arranged in a ring, midway 

 between the centre and the periphery of the cell, but sometimes they nearly fill the 

 whole cell. Occasionally the giant cells have vacuoles. Erythroblasts and nucleated 

 red cells are numerous ; the perinuclear protoplasm of both stains faintly, if at all, 

 with eosine, and seems to be practically destitute of haemoglobin. There are a few 

 coarsely granular protoplasmic corpuscles present, some of which are vacuolated, and 

 numerous pigment-holding cells. 



Results of Experiments. 



It seems, therefore, that upon the induction of the anaemic state in dogs the spleen 

 reverts to its early condition, that characteristic of early extra-uterine life. And the 

 number of giant cells in the spleen appears to vary directly with the number of erythro- 

 blasts and nucleated red cells in it, and to some extent with the number of nucleated 

 red cells in the blood ; but giant cells may be present in the spleen without any nucleated 

 red cells occurring in the blood of the splenic vein. 



In my experiments the spleen was not found to be remarkably swollen, or to have 

 the rose-pink colour described by Bizzozero and Salvioli ; but the spleens of Dr Muir's 

 experiments were much more swollen, and it seems probable that those appearances 

 co-exist with the higher degrees only of haematopoietic activity. 



That many nucleated red blood-corpuscles are found in the red bone-marrow, and 



VOL. XXXVIII. PART II. (NO. 8). 2 T 



