316 THE ANEMIAS 



lymphoid marrow, these changes including sometimes smaller, sometimes 

 larger, portions of the bone-marrow. If, in a case of simple anemia, we were 

 to examine such a portion microscopically, an exact picture of the normal 

 lymphoid marrow would be seen, such as is always found in the ribs, the verte- 

 brae, the sternum, and is besides characterized by the presence of white cells 

 (which we do not take into consideration), and by red blood-corpuscles of the 

 same size as the erythrocytes of normal blood, some without, some with, nuclei. 

 But the picture we obtain in cases of progressive pernicious anemia of all, 

 or of many, of these transformed red bone-marrow regions is entirely differ- 

 ent. The nucleated, as well as the non-nucleated, red blood-corpuscles are of 

 such a size, and contain such a rich quantity of hemoglobin, as is never ob- 

 served in the bone-marrow of the normal adult but only in the embryo. These 

 differences seem to be so essential as to necessitate a special classification of the 

 anemias, even if thoy did not bear out what we should expect from the clinical 

 symptoms and the condition of the blood. 



In progressive pernicious anemia the whole fat marrow very rarely degen- 

 erates into lymphoid megaloblastic marrow, and this is a factor which enables 

 us the better to comprehend certain variations in the blood findings, and is of 

 the greatest importance in practical diagnosis. Often only a portion of the 

 lymphoid marrow shows a megaloblastic structure, while the other regions are 

 lymplio-normoblastic. Moreover, only a part of the fat marrow is diseased 

 in most cases. Of course, the number of megaloblasts and megalocytes con- 

 tained in the circulating blood depends upon the size of the megaloblastic por- 

 tion of the bone-marrow, and other temporary variations in the composition 

 of the blood may be thus explained. 



It is our purpose to discuss in this article only points of practical impor- 

 tance. But we must not forget that a series of questions most intimately 

 related to the changes in the bone-marrow are still awaiting solution. For 

 bothriocephalus anemia, the correct explanation has probably been given, and 

 most authors of the present day maintain the view that the toxin of the bothrio- 

 cephalus causes the specific megaloblastic changes of the bone-marrow. This 

 gives us a hint as to the etiology of other types of progressive pernicious ane- 

 mia, and inclines us to the general supposition of a specific toxic influence. 

 It is more difficult to answer the question as to what particular circumstances 

 transform a simple anemia into the megaloblastic form, an occurrence which 

 must certainly be considered infrequent considering the prevalence of simple 

 anemia. At present, the toxin hypothesis does not sufficiently explain the 

 extraordinarily rare cases in which progressive pernicious anemia develops as 

 the consequence of a simple posthemorrhagic anemia. 



But it cannot be disputed that progressive pernicious anemia may develop 

 from a simple anemia, and this confirms the view that there must be transi- 

 tional stages in which it is exceedingly difficult, and often even impossible, to 

 determine to which class of anemias a given case belongs. Still, we meet with 

 such transitions and intermediate stages within the whole domain of pathol- 

 ogy, in fact in all departments of natural science ; they must not, therefore, 

 be an obstacle to the differentiation of the fulhj developed Jorms, nor are they 

 proofs of the non-existence of special types of the disease. 



