MICROSCOPIC STRUCTURE OF THE BLOOD. 271 



nucleated disks, having an average diameter of 7.7 //, some of 

 them being as small as 4.5 //, while others are 9 //. The small 

 corpuscles are termed mieroeytes, and are regarded as not fully de- 

 veloped corpuscles. In chronic anemic conditions some have been 

 found as large as 14 p, and others as small as 2.2 jut. 



Number of Red Corpuscles. The number of red corpuscles in 

 a cubic millimeter of the blood of a male adult has been reckoned 

 at 5,000,000 ; in that of a female, 4,500,000. In a man weighing 

 68 kilos there are estimated to be 25,000,000,000,000, present- 

 ing a superficial area of about 3200 square meters. In all the 

 blood of the body in health their number is consequently enormous. 



There are various methods of determining the number of red 

 corpuscles: (1) By the hematocrtt (p. 270); (2) by the hemacy- 

 tometer. 



By the Hematocrit. This instrument has been described, and 

 its use explained, for determining the relative proportion of cor- 

 puscles and plasma. It has been ascertained that each volume of 

 corpuscles, as indicated by the scale, represents 97,000 corpuscles. 



FIG. 144. Blood-corpuscles : a, blood-plaques or third corpuscles ; 6, red corpuscles ; 

 c, white corpuscles (Eberth and Schimmelbusch). 



By the Hemacytometer. There are three forms of this instru- 

 ment that of Gowers, that of Thorna-Zeiss, and that of Oliver. 



Gowers 9 hemacytometer consists of a pipet, which contains 

 995 cu.mm. when filled to the mark made on the tube, a 

 glass mouthpiece is connected with this pipet by means of 

 rubber tubing; a capillary tube, holding 5 cu.mm. when filled 

 to the mark, this also having a mouthpiece and rubber tubing ; a 

 brass plate, with a glass slide, on which is a cell having a 

 depth of ^ mm. and divided on the bottom into y 1 ^ mm. squares, 

 the cell in use being covered by a cover-glass ; a jar, in which 

 the blood to be examined is diluted ; a glass rod, for staining ; 

 and a needle, for pricking the finger to obtain blood. 



A solution of sodium sulphate is made having a specific gravity 

 of 1025, which corresponds to the specific gravity of blood-plasma, 

 and this is sucked up into the pipet to the mark indicating 

 995 cu.mm. This is then deposited in the jar. The finger is 

 pricked with the needle, the amount of projection of which can be 

 regulated by a screw, and 5 cu.mm. of blood sucked up into the 

 capillary tube, and this is then deposited in the jar with the saline 

 solution, and the mixture thoroughly stirred with the glass rod. 

 A drop of the mixture is then placed in the cell and a cover-glass 



