93 



gîobin cells (perivascular foci of erythro- 

 blasis (normoblasts) (v. Plate 21, Fig. 

 11). 



The reconstitution of the fat-con- 

 tents of the fat-cells continues (v. Plate 



21, Figs. 9, 10 and 11). The lymphocy- 

 tes become rarer, the character of a 

 diffuse infiltration which they showed 

 disappears; megalocaryocyles in pro- 

 nounced phagocytic activity. Discrete hy- 

 perplasia of the fixed connective tissue 

 cells (fibrosis) (v. Plate 20, Fig. 8). 



5th, 6th and 7th Days. 



The congestion of tlie capillaries 

 shows a tendency to disappear and the 

 œdema of the reticulum is becoming 

 reabsorbed. Hyperplasia or intense pio- 

 liieralion of myelocytes, grouped round 

 the vessc's i;i a conspicuous manner (Pla- 

 te 22, Fig. 13 and Plate 17, Fig. 16); active 

 evolution ofmye'ocyles into polymorpho- 

 nuclear leucocytes, with individual varia- 

 tions with regard to tlie numerical pre- 

 dominance of one kiid of cell over the 

 other. Fat-cells reJuced in volume; some 

 of them, however, have already reac- 

 quired their original dimensions (Plate 



22, Fig. 12); others are hidden by the 

 myelocytes in hyperplasia (v. Plate 17, 

 Fig. 16). Numerous small foci of fibro- 

 sis (proliferation of connective tissue 

 cells) probably representing the organi- 

 sation of small hiEmorrha-,ic foci (v. 

 Plate 20, Fig. 7). 



7th Day. 



Capillary congestion only in a few 

 points, oedema of reijulum has already 

 undergone resorption; round the fat-cells 

 there has deposited itself a substance 

 with the caracters of hyaline substan- 

 ce. Parenchyma with an active regenera- 

 tion of celts, not only of the more nu- 

 merous cells of the myeloid series, but 

 also of the hsemoglobin-contaiaing ele- 

 ^xneats. 



14th Day. 



Bone-marrow in marked hyperplasia, 

 the most numerous cells being myelocy- 

 tes and polymorphonuclear leucocytes. 

 Owing to the hyperplasia of the cells 

 of the myeloid series, the fat-cells are 

 not conspicuous. A specially interesting 

 fact is the existence of foci with the 

 structure of lymphoid follicles and pos- 

 sessing a germ-centre (v. Plate 17, Fig. 

 17). Megalocaryocyles with pronounced 

 phagocytic activity. 



Condensing the facts, we may say 

 that in the course of immunisation for 

 the obtention of agglutinins, the bone- 

 marrow undergoes, right in the first 

 hours, a marked reclu- tion in the num- 

 ber of its cells, with intense congestion 

 and œdema of reticulum and regressive 

 alterations in the parenchyma cells. A 

 remarkable fact is the suljsequent loss 

 of the fat-conlents of fat-cells, preceded 

 by the dispo>>i ion of polymorphonuclear 

 leucocytes round them like a crown. The 

 reduction in volume of the fat-cells ap- 

 pears to be frerpient in difiercnt patholo- 

 gical states of the bone marrow, but the 

 chemo'.axis of polymorphonuclear leuco- 

 {•ocyles for the fat-cell had not yet been 

 (les ri ed an.d oily subsequent research 

 wil show whether it is a lesion peculiar 

 to bone-marrow or not. 



After this initial period, there is 

 gradual regeneration of tlie different 

 cells; before this the bone-marrow is 

 the seal of an inl'iltration by cells with 

 all the charade s of blood-lymphocj'lcs; 

 this invasion pre-.eJes the phase of re- 

 generation of the myelocytes and cells 

 of tlie luvmoglahin-conlai ,ing series and 

 this cinious observations might be of 

 great theoretic importance. 



The fal-conlents of fat-cells are gra- 

 dually rehuill. 



Lalcr on, on the 6th day of immuni- 

 sation, the most noticeable his o!ogic alte- 

 ration is an inlense hyperplasia of the 

 pareuchyma-cells; mitotic figures of di- 



