130 



MANUAL OF HISTOLOGY. 



into the amoeboid lymph-cells of the splenic tissue, the corpuscles and 

 their fragments may give rise to the formation of those cells containing 

 blood-corpuscles observed in the spleen. The same may also take place 

 possibly in the medulla of bones. 



We may mention here another circumstance for the discovery of which 

 we are indebted to Strieker, namely, that by impeded circulation and 

 increased pressure the red cells of the blood are forced through the unin- 

 jured walls of small vessels (capillaries and veins). Thus partly unin- 

 jured, partly divided into small beads, in consequence of being obliged 

 to squeeze through, they reach the exterior, and are found in the neigh- 

 bouring tissues and adjacent lymphatic passages according to Herirtg. 

 In the first position they probably decay very rapidly, while their occur- 

 rence in the latter explains, at least partially, the presence of red blood- 

 corpuscles in the lymph, already long known. 



It is only seldom that under normal conditions blood escapes into the 

 tissue of any living organ from lacerated vessels; but we have one case, 

 that of the ruptured Graaffian vesicle. Such extravasations, however, are 

 not of unfrequent occurrence pathologically. In both these cases we meet 



Fig 124. Blood-vessels of the frog's mensentery, eight hours after irritation Had "been set up, showing 

 emigration of lymphoid cells. A, a large capillary, shows at a, the mode of escape of cells, at 6, some 

 already escaped. B, a vein ; o, the lymphoid cells closely applied to the walls, and making their way 

 through; 6, external to the vessel; c, coloured blood-corpuscles. 



with destruction of the coloured elements after coagulation, and production 

 from them of haematoidin crystals. In such effusions of blood, also, we 

 may again meet with those cells already mentioned containing blood- 

 corpuscles. 



The colourless cells derived from the medulla of bones, the spleen, and 

 lymphatic glands, are now looked upon, and indeed rightly, as serving 

 to replace the loss of the red corpuscles ( 71). 



But in what proportion these undergo transformation into the latter is 

 not yet ascertained, and is dependent upon the length of existence of the 

 red cells, still completely unknown. However, we cannot doubt that such 

 a metamorphosis of white corpuscles into red does take place very exten- 

 sively after severe losses of blood, where a rapid reparation occurs. 



But these lymph-corpuscles have yet another destiny. 



