COUNTING THE RED BLOOD CELLS. This is best accomplished by means of Thoma's Inematocyto meter or blood-counting apparatus. This consists of a pipette with bulb and graduated capillary tube. The graduation of the tube is 0.5 and 1, that of the bulb and tube together 100. By filling the tube to mark 1 with blood and then the bulb and tube to mark 100 with an inert diluting fluid such as normal saline, a dilution of 1 to 100 is obtained. The counting slide has in its centre a round chamber, in the centre of which is a raised flat glass surface which is marked off into 400 equal squares, each of which is one four-hundredth of a square millimeter. The surface of the marked-off area is just one-tenth of a millimeter lower than the surface of the rest of the slide. A drop of the diluted blood is placed upon the centre of the graduated area and a flat cover glass placed over it. As will be seen, the amount of fluid over one of the small squares is one-tenth times one four-hun dredth or one four-thousandth of a cubic milli meter. The number of cells in one square is then counted. This multiplied by 4000 and then by the dilution, 100, gives the result desired, i.e. the number of red cells in one cubic millimeter of blood examined. In actual practice a large number of squares is counted and the average taken. The white blood cells may be counted in the same specimen if desired. ()wing. however. to their smaller number, a larger number• of squares should he counted to avoid error. For determin ing the of the individual eorpuseles in luemoglobin, the shape and size of the cells. the relative number of the different kinds of white cells, the presence of the malaria plasmodium. etc., the preparation of fixed and stained speci mens is required as follows. Blood from a needle prick is taken up on the end of a glass slide and this is drawn across the surface of a second slide, thus making a thin 'smear' of blood. This is dried quickly in the air, after which it is 'fixed' by equal parts of alcohol and ether, the vapor of °smite acid or of formalin. or by subjecting to the action of dry heat. The specimen is now ready for staining. A combination of eosin and methylene blue, and Ehrlich's triacid stain, are the most satisfactory. After staining the speci men is washed in water. The eosin-methylene blue method is the most satisfactory for general purposes and stains the malaria plasmodium. Ehrlieh's stain is most satisfactory for making a differential count of the leucoeytes.
Persistent marked reduction in the number of red cells occurs in primary pernicious anemia and in the secondary due to sonic of the infectious diseases. It may also be due to the action of certain mineral poisons (phos phorus, arsenic, etc.), to long-continued suppura tive processes. cancer, malaria, conditions of malnutrition, etc.
Loss in the hemoglobin content of the indi vidual cells occurs especially in that form of anemia known as chlorosis. Moderate diminu tion in number of cells may also occur. In len eoeytlnemia there may also be both a reduction in the number of cells and a reduction in Immo globin content. This loss on the part of the indi vidual cell in hemoglobin is shown in the eosin stained specimen by an inerease in the clear cen tral area of the cell.
Irregular red cells (poikiloeytes), small red cells (mieroeytes), and large red cells (megalo eytes) are found in severe anemias whether pri mary or secondary.
.Nucleated red blood cells are found in all forms of anemia. As they represent developmental types, their presence may be construed as an attempt on the part of nature to replace lost cells. Very large nucleated red cells (megalo blasts and gigantoblasts) are sometimes present in severe anamias.
Moderate increase in the number of white blood cells occur; phy:inlogically during the first few days after birth. in the later months of preg nancy, and after eating. Pathologieal inerea;e in the number of white cell; (welly; in many of the infectious diseases, especially those accompanied by exudation or suppuration. It is notably ab sent in typhoid, typhus. tuliereulo.d;. mea;les, and malaria. Lymphoeytosis. or increase in the num her of lymphocytes, is frequent in the later weeks of typhoid. in anemia, in intestinal diseases of children, and in lymphatic leucocythamiiii. Per sistent increase in the number of white blood cells independent of other lesions is characteristic of leueocytlemia. This increase may be very great, and is usually irregular, i.e. the proportionate numerical relation of the different kinds of white blood cells is changed. ]n lymphatic leueocy thiemia the greatest increase is in the lymph ocytes. In myelogenous leueocythirmia the in crease in leucocytes is often enormous, sometimes more than a million per cubic millimeter. Ab normal forms of leucocytes also appear.