78 



stained iti híemaloxylin-eosin and fluid 

 GIEMSA. 



Cellular contents of marrow appro- 

 ximalelj^ normal. 



Capillary congestions remains very 

 marked Fig. 9. PI. 21). 



The œdema has suffered resorption 

 and is only to he seen here and there 

 in an inconspicuous manner. 



The most abundant cells are ampho- 

 phil myelocytes and polymorphonuclear 

 leucocytes Fig. 10, Plate 21); some mye- 

 locytes show mitotic figures and dispose 

 themselves in foci. 



Conspicuous foci of division of ery- 

 throblasts (normol)lasts ^ are to be seen, 

 some of them not only in the middle of 

 the parenchyma, but also round the 

 medium-sized vessels and prae-capillaries 

 (Fig. 11, Plate 21). 



The diffuse infiltration of the pa- 

 renchyma by cells with the appearance 

 of honphocvtes is evident. (Fig. 9, Plate 



21)/ 



The fat-cells show the same appea- 

 rance as in rabbit 211. 



Almost ail megalocaryocyles contain 

 in their protoplasm some polymorpho- 

 nuclear leucocytes; some megalocaryocy- 

 tes show regressive changes. 



The similarities and differences bet 

 ween the ones here described (3rd day 

 of immunisation) and the previously in- 

 dicated ones are the following: 



Tere is a begiimir.g resorption of the 

 œdema of the reticulum. 



The bone-marrow is almost as rich 

 in cells as under normal conditions, the- 

 se cells are principally myelocytes and 

 polymorphonuclear leucocytes. 



Foci of regeneration of hscmoglo- 

 bin-containing elements (perivascular fo- 

 ci of erythroblasts (normoblasts) ) begin 

 to appear. 



Regeneration and replacement of fal- 

 «ontents of fat-cells continues. 



Lymphocytes become scarcer and loo- 

 se the appearance of a diffuse infiltra- 

 tion. 



í.íegacaryocytes show a pronounced 

 phagocytic activity and imdergo proces- 

 ses of désintégration. 



3rd. Day of Immunisation. 



Rabbit 216. -Weisbt 1,300 grt. 



Inoculated in marginal vein of ear with a sterilised 

 B. paratyphi A. emulsion (emulsion A) at 3.30 p. m. on 

 April 7 th 1920. 



Killed at 12.50 p. m. on April 10 tli 1920 (72 grs, 

 and 20 mins. after inoculation). 



Autopsy canned out at once. 



Autopsy — Bone-marrow (femur) with 

 normal soft consistency and dark red 

 colour. Disseminated spots of a whitish 

 colour are to be seen. 



Microscopic study. — Sections fi.xed in 

 ZENKER-formol stained in haematoxylin- 

 eosin and fluid G1EMS.\. 



I'nder a weak jwwer congestion of 

 capillaries, œdema of reticulum, reduc- 

 tion in parenchyma cells, disappearan- 

 ce of fat-cells and increase of fixed 

 connective-tissue cells (Fig. 3, Plate 20), 

 the latter dicreased are to be observed. 



.\ strong power shows that the do- 

 minant cells are myelocytes and leuco- 

 cytes; there is also a diffused but not 

 intense infiltration of cells with the ap- 

 pearance of lymphocytes. 



Myelocy/es are frequently found in 

 little groups of 2, 3, 4 or 8,. rarely of 

 more cells; the most numerous groups 

 are the ones of 4 (Fig. 6, Plate 20). 



The bone-marrow shows an evident 

 decrease in number of cells. 



These cells are found close to tlic 

 capillai'ies. 



This perivascular distribution of mar- 

 row cells (in this case polymorphonuclear 

 leucocytes and myelocytes) in this rabbit 

 can be looked upon as a striking exam- 

 ple. 



Tiie fat-cells are not in evidence; 

 in their protoplasm no fat-containing va- 

 cuole is visible; limits of protoplasm are 

 indistinct and merge into the oedema- 

 fluid of reticulum. These cells arc onl>' 

 recognisabe by the structure of their 



