77 



Under a strong power one noti- 

 ces that the most numerous cells are 

 amphophil myelocjtes and polymorpho- 

 nuclear leucocytes, there being also 

 foimd amongst them, looking like a dif- 

 fused infiltration, small cells with nuclei 

 very rich in chromatin and resembling 

 blood lymphocytes in their morphology. 



The megalocaryocytes are not found 

 in reduced number; their nucleus ap- 

 pears well-stained and with its normal 

 structure. 



Many of the megalocaryocytes found 

 enclose one or more leucocytes in their 

 protoplasm. 



The fat cells are found reduced in 

 volume, the fat-containing vacuole is 

 smaller than in similar cells of nor- 

 mal bone-marrow; in many cells this 

 reduction amounts to one half or one 

 thii'd of normal volume, and, not infre- 

 quently, in others to one tenth of nor- 

 mal volume. 



In cells whose vacuole is reduced 

 to one half or one third, the nucleus 

 retains its peripheric position and its 

 normal appearance. The nucleus of cells 

 reduced to one tenth of their volume is 

 more evident, as it becomes tumid and 

 vesicular; this kind of cell does not 

 show pyknosis or any other aspect indi- 

 cating regressive changes. 



The appearance described for the 

 fat-cells of rabbits 212 and 210 (enlarged 

 nucleus, wifti a tendency to leave its 

 excentric position and surrounded by a 

 zone of protoplasm with an evidently 

 reticular structure) was only rarely seen 

 in tliis rabbit. 



The lesions fomid in the bone- 

 marrow of rabbit 214, killed 46 hrs 30 

 mins. after the commencement of im- 

 mimisation can he seen in the following 

 résumé : 



1°) Congestion and œdema of reticu- 

 lum. 



2°)Slight reduction in number of the 

 cells of the medullary parenchyma; am- 

 phophil myelocytes and polymorphonu- 



clear leucocytes predominate; the last 

 are found in their normal number, but 

 appear more numerous on account of 

 the reduction in number of the cells. 



3o) Dispersed infiltration of paren- 

 chyma with cells of the appearance of 

 blood lymphocytes. 



4o) Megalocaryocytes normal in num- 

 ber and in appearance many of them 

 containing one or more polymorphonu- 

 clear leucocytes. 



5o) Fat-cells fewer and smaller than 

 in normal bone-marroiv, with a nucleus 

 of normal appearance; some other fat- 

 cells very much smaller (one tenth and 

 even less of normal volume). 



The appearance of the fat-cells I 

 believe to indicate a stage of recons- 

 truction or recomposition. After the loss 

 of fat observed in the first 24 hours of 

 immunisation and which is indicated by 

 a special appearance of the cell (see des- 

 cription rabbit 212), these cells begin 

 to regain fat-contents. 



3rd. Day of Immunisation. 



Rabbit 450-Weight 1.150 grs. 



Killed 60 hours after inoculation. 



Feb. 5 th 1920— Leucocytes : 12.15 p. m.=8000 per 

 rams. 



Inoculated at 4 p. m. in the marginal vein of ear 

 with 1 cc. of saline solution with a loopful (2 niilligrs.) 

 of a 24 hours' agar-agar culture of B. paratyphi A. in 

 suspension. The suspension was sterilised by heating in 

 a water-bath at 60oC. during 1 hour 30 mins. 



Feb. 26 th 1920— Leucocytes ill a. m.)=33.400 per 

 mm3. 



Feb. 27 th 1920— Leucocytes (3.30 p. m.)=34.800 per 

 mm3 



Feb. 28 th 1920. 



Found dead in the morning. 



E.xamined under good conditions of preservation. 



Aü/opsy — Bone-marrow soft, difflu- 

 ent, of a dark red colour; in the centre 

 (in the part corresponding to tlie lengUi 

 diameter) a dark-red and strong cord 

 stands out from the medullary paren- 

 chyma (central vessels of bone-marrow). 



Microscopical siady.— Section of the 

 material fixed in ZENKER-formol an(i 



