92 



Tery probable, this fact would have a 

 special interest, since it would show the 

 possibility of lymphoid follicles with a 

 quite evident germ-centre occurring in 

 the bone-marrow (Fig. 17, Plate 17). 



In normal rabbits only occasionally 

 did I find lymphocytes, which were al- 

 ways isolated. The existence of lymphoid 

 follicles in the bone-marrow of the adult 

 rabbit is, according to me, a patholo- 

 gical condition. Might not the expression 

 of dijmphoid metaplasia>y in this case 

 be not altogether vmsuitablo. 



IV — Conclusions. 



It is quite common to observe his- 

 topathological lesions of the bonemarrow 

 of apparently healthy rabbits; of these, ho- 

 wever, the niunbcr of leucocytes is al- 

 most always abnormal. SELLING'S re- 

 commendation, i. e. to observe during 

 a period of 3 consecutive days the num- 

 ber of leucocytes and exclude the rab- 

 bits that, during this time show consi- 

 derable daily variations or an al)nonnal 

 number, proved very useful. 



I carried out a histopathological stu- 

 dy on the bone-marrow of 40 rabbits 

 immunised for the obtention of aggluti- 

 nins (B. paralijphi A) 



I ascertained the existence oí le- 

 sions succeeding each other witîi great 

 regularity; this process can be divided 

 according to its morphological charac- 

 ters into the following phases: 



4 hours of immunisation. 



Slight congestion, inconspicuous oede- 

 ma of reticuliun and a modification (di- 

 sorder) in the normal arrangement of 

 the parenchyma cells which are less 

 numerous than under ordinary condi- 

 tions and above all an intense trans- 

 formation of myelocytes into polymor- 

 phonuclear leucocytes. These polymor- 

 phonuclear leucocytes, dispose themsel- 

 ves after the fashion of a crown round 

 jRome fat-cells and make up a little 



fociis round one of them (s. Figs. 11 

 and 15, Plate 17). The aspects observed 

 show a pronoimced chemo taxis of the 

 fal-cells for the polymorphonuclear leu- 

 cocytes. 



17 to 36 hours. 



Marked congestion and pronounced 

 œdcma of reticulum (s. Fig. 3, Plate 

 19). Considerable reduction in the num- 

 ber of parenchyma cells (aplasia) (s. 

 Figs. 3 and 4, Plate 19), with almost 

 complete disappearance of the polymor- 

 phonuclear leucocytes. Pronounced re- 

 gressive changes in the myelocytes and 

 megalocaryocytes (Fig. 5, Plate 19). Mul- 

 tiplication of amphophil myelocytes, in 

 its first stages, constituing little foci 

 of 3-4 discrete and rare cells. 



Reduction in volume of fat-cells (v. 

 Plate 19, Fig. 3), whose nucleus showing 

 the fine structural details, is slightly 

 tumefied and displaced towards the cen- 

 tre of the cell (v. Plate 19, Fig. 4); the 

 protoplasm all around has a clearly re- 

 ticular structure. Finally, a diffuse infil- 

 tration of leucocytes (v. Plaie 19, Fig.^ 

 4). 



2nd Day. 



There is persistance of the conges- 

 tion, oedema of reticulum, and diffuse 

 infiltration of leucocytes, also regene- 

 ration of the polymorphonuclear leuco- 

 cytes and perhaps a slight excess of 

 them. Reconstitution of the fat-contents 

 of the fat-cells. 



3rd Day. 



The resorption of the cedema of the 

 reticulum begins. The congestion of ca- 

 pillaries persists (Plate 21, Fig. 9). The 

 parenchyma cells, as abimdant as in 

 the normal state, are chiefly myelocytes, 

 disposed in small foci of 2, 4 or more 

 cells (Plate 20, Fig, 6) and polymorpho- 

 nuclear leucocytes. There begin to ap- 

 pear foci of regeneration of the h«mo- 



