234 CLINICAL BACTERIOLOGY AND HEMATOLOGY 



normal red corpuscle. If you look at the squares with a central 

 ruling, you will be able to compare any corpuscles which may be 

 in them with the semi-diameter ; the one should be one-third of 

 the other, and you may consider' as a megalocyte any corpuscle 

 which is one-half or more of this semi-diameter. 



3. Poikilocytes (Plate VIII., Fig. 6) are deformed corpuscles, 

 and are typically shaped like a pear, but may be kidney-shaped 

 or quite irregular. They may be about as large as a normal 

 corpuscle, or smaller, or larger, and they may stain abnormally. 

 Poikilocytes are more common in pernicious anaemia than in 

 other diseases, but are not of much diagnostic importance, since 

 they only occur in advanced stages of the disease, long after the 

 diagnosis should have been made. To recognize them, put a 

 small drop of blood on a perfectly clean slide, apply a cover-glass, 

 and examine at once ; do not identify poikilocytes in dried films 

 or in the counting-chamber of the haemocytometer until you have 

 had a good deal of experience, as accidentally injured and con- 

 torted forms may occur in either. 



4. Polychromasia, or, as it was formerly called, Polychromatopkil 

 Degeneration (Plate VIII., Fig. 3). — In this condition the corpuscle 

 (which may be normal or abnormal in other ways), instead of 

 being strictly acidophile in its staining reactions, stains with the 

 basic stain to a greater or less extent ; thus, with Jenner's stain 

 it stains a variable mixture of pink (from the eosin) and blue 

 (from the methylene blue). It may be lilac, purplish, or almost 

 pure blue. The change is readily recognizable in ordinary films 

 stained by Jenner's method. 



The corpuscles are now thought to be new and imperfectly 

 matured forms : they were formerly regarded as degenerations. 



They are especially common in pernicious anaemia and in von 

 Jaksch's anaemia of children, but may occur in almost any form 

 of anaemia, if very severe. They do not form a very important 

 diagnostic feature, but their presence always constitutes a bad 

 sign. 



5. Granular degeneration (Plate VIII., Fig. 2) takes the form of 

 numerous granules of varying size, which occur in the red cor- 

 puscles, and which stain almost black with the basic portion of 

 the stain ; the rest of the corpuscle often shows polychromatophil 

 degeneration. 



It occurs also in any severe anaemia, especially in von Jaksch's 

 anaemia, where corpuscles in which it occurs may be extremely 



