CHAPTER VI 

 SPECIAL DISEASES OF THE BLOOD 



PERNICIOUS ANEMIA 



This term has been applied to an entirety different condition 

 in horses from the affection known by the same name in human 

 medicine. In human medicine the distinction between anemia of 

 the pernicious type and secondary anemia, is based on several 

 criteria, of which the more important are the high Hb index, the 

 presence of a large number of megalocytes (at least 33%) or, when 

 erythroblasts are present, an excess of megaloblasts over normo- 

 blasts. Pernicious anemia has been defined as a severe anemia for 

 which the cause is unknown or wholly inadequate to produce so 

 serious results in the organism. More recently it is defined by the 

 blood picture which shows a greater number of megaloblasts than 

 normoblasts or at least 33% megalocytes. The essential lesion is 

 a megaloblastic hyperplasia of the lymphoid marrow. The term 

 has been applied to a disease in horses producing a severe anemia 

 of which the cause is obscure. The blood picture is, however, 

 quite different from that presented by pernicious anemia in man, 

 being rather that found in a secondary anemia. 



In pernicious anemia in man the red corpuscles are much 

 diminished in number. Megalocytes with increased hemoglobin 

 comprise from 33-90% of the red corpuscles; but may be few dur- 

 ing the periods of remission. Megaloblasts are few or numerous, 

 but are more numerous than normoblasts; microblasts are scarce. 

 The hemoglobin index * varies but is usually one or higher. It 

 may be below the normal during remissions or in the early stages 

 of the disease. Coagulation is slow, rouleaux do not form, and 

 there is lessened resistance of the red corpuscles. Poikilocytosis, 



* The hemoglobin index, or color index, is the relative amount of hemo- 

 globin contained in each corpuscle and is obtained by dividing the percentage 

 of hemoglobin by the percentage of corpuscles. In human blood the normal 

 number of corpuscles is considered as 5,000,000, which is 100%. 



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