FALLACIES AND PUZZLES IN BLOOD EXAMINATION 119 



A blood plate resting on a red cell may, as in fresh blood, cause the inexpert to diagnose 

 malaria, but the fact that it has no blue-staining protoplasm, that its chromatin is 

 deep red, irregular and granular, that its outline as a rule is somewhat indefinite, 

 and that generally it has pushed the haemoglobin away from below it and consequently 

 produced a ring-shaped, non-staining area around it should prevent the error (Plate VII., 

 fig. 2). A mass of platelets has before now been mistaken for a crescent or a clump of 

 spores, but the staining reactions and the lack of pigment should leave no room for doubt. 

 I have seen platelets which required a little careful observation to be sure they were 

 not Leishman-Donovan bodies, for they sometimes show dark chromatin rods very like 

 blepharoplasts, but one is guided correctly by much the same considerations which 

 weigh with one in distinguishing them from malarial plasmodia. Their reticular structure 

 is, I think, on the whole, the surest guide to their identity. Osmic acid fixation 

 probably preserves their form better than any other method. 



In animal blood the platelets may assume confusing forms as may be seen by reference Platelets 

 to Plate XV. of our Second Report where flagellated and blue-staining forms are seen. 

 A little experience soon sets one right. The same thing applies in a lesser degree to 

 the platelets in equines. It is not, I think, necessary here to enter into the question of 

 true and false platelets and the so-called Arnold's bodies, but as a red cell is often seen 

 apparently extruding platelets — an appearance which may confuse a beginner — it is worth 

 noting that Hugh Eoss states that this phenomenon is never apparent when blood is 

 examined by in vitro methods. He has also drawn attention to the presence of diffusion 

 vacuoles in platelets which appear as red spots when stained. In fowls, the so-called 

 thrombocytes take the place of platelets, and as they are quite large cells and may stain 

 quite deeply by the Eomanowsky method, I have known them mistaken for haemogregarines 

 [Third Report, Plate V., fig. 2). I cannot do better than quote the description given bj' 

 Burnett of these spindelzellen, as von Eecklinghausen named them, especially as I find very spindehelUn 

 few people, even those accustomed to blood work, seem to recognise them as a distinct 

 entity. They are most likely to be mistaken for distorted lymphocytes. 



Burnett describes them as "elliptical, oblong or spindle-shaped cells with an elliptical 

 to broadly oval nucleus. In size the cell has nearly the length and about one-half the 

 width of the average red cell. The nucleus occupies about one-half the length and nearly 

 the entire width of the thrombocyte and is usually situated in the central part of the cell. 

 The cell body is pale and often contains one or more clear vacuoles and occasionally one or 

 more compact, rounded, deeply staining (deep purple with Wright's stain) bodies about the 

 size of, or somewhat larger than, a mast cell granule. These bodies are probably a result 

 of degeneration. The thrombocytes show a marked tendency to collect in clumps. In 

 fresh blood and in the less thinly spread parts of films, they collect in masses in which it is 

 difficult to distinguish the outline of individual cells. This indistinctness of cell outline and 

 structure shows another property of these cells, that is their vulnerability. They change 

 quickly when taken from the blood vessels, passing through a characteristic series of 

 changes. Both cell body and nucleus become less distinct, the cell body losing its structure 

 first. Finally, both become structureless, appearing in stained preparations merely as a 

 diffusely stained mass, the nucleus being distinguishable by having a slightly deeper stain." 



Turning now to the red cells, alterations in shape and size need not long detain us, Alterations in 

 for all the ordinary changes are fully dealt with in the standard works on the blood and 

 are, or should be, known to every medical student. When, however, an observer for 

 the first time encounters in the blood of a fowl forms like Plate YI., figs. 6 and 7, he is 

 apt to be puzzled although they are merely distorted and enucleated erythrocytes which 



