CHAPTER II 

 MORPHOLOGY OF THE FORMED ELEMENTS 



RED CORPUSCLES (ERYTHROCYTES) 



In the circulating blood these elements have a cup shape in 

 man, horse, cow, sheep, dog, cat, rabbit, guinea pig (Weidenreich, 

 Lewis) and presumably in other domesticated mammals excepting 

 camels. This shape may be seen in the counting chamber when 

 Toisson's fluid is used as a diluent, or when blood is examined in 

 physiological salt solution; but better when examined in a 2.5 to 5% 

 solution of sodium metaphosphate freshly prepared. Ordinarily 

 when examined in the fresh condition or in dried preparations 

 the red corpuscles appear as bi-concave discs of a pale straw color, 

 the color being deeper in the peripheral part of the disc and nearly 

 absent in the central part. The size of this central clear area 

 varies in different conditions. In cases of anemia it may be rela- 

 tively large. The red corpuscles in mammals are not nucleated 

 as a rule in the circulation except during the intra-uterine period. 

 Small numbers of nucleated red cells may be found in the cir- 

 culating blood in the young. In the domestic fowl the red cor- 

 puscles are elliptical nucleated cells. The size of the red cor- 

 puscles varies with the different species of animal. The averages 

 for each animal will be found in the tabulated summaries in Chap- 

 ter III. In stained preparations the red corpuscles take the acid 

 stain, the difference between the central clear area and the deeper 

 colored peripheral part being clearly shown. In pathological 

 conditions marked changes in the size, shape and staining proper- 

 ties are sometimes shown. Instead of being about the same size, 

 marked variation may appear in cases of anemia. It is to be noted 

 that in the young there is normally a considerable variation in 

 size. Very small corpuscles, about one-half the average size are 

 called microcytes. Corpuscles one-half larger to twice the diameter 

 of the average are called megalocytes. In anemia corpuscles of 

 various shapes may be found, the most usual being pear shaped. 

 These are called paikilocytes and the condition is known as poi- 



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