ENUMERATION OF THE BLOOD-OOKPUSCLES. 



11 



The blood to be examined is diluted with ninety-nine parts of a liquid composed of 

 one volume of a solution of gum-arabic of a specific gravity of 1020 with three volumes 

 of a solution of equal parts of sulphate of soda and chloride of sodium, also of a spe- 

 cific gravity of 1020. The mixture, containing one part of blood in one hundred, is in- 

 troduced into a small thermometer-tube with 

 an elliptical bore, the sides of the tube being 

 ground flat for convenience of microscopical 

 examination. The capacity of the tube is to 

 be calculated, by estimating the weight of a 

 volume of mercury contained in a given 

 length. The tube is then filled with the di- 

 luted blood, and the number of corpuscles in 

 a given length of the tube is counted by 

 means of a microscope fitted with an eye- 

 piece micrometer. In this way, the number 

 of corpuscles in a given volume of blood can 

 be readily estimated. In man, the number 

 in a cubic millimeter of blood (a millimeter = 

 about ^ T of an inch) is estimated at about 

 four million. 



According to the observations of Malas- 

 sez, the proportion of corpuscles is about the 

 same in all parts of the arterial system. In 

 the veins, the corpuscles are more abundant than in the arteries. In the venous system, 

 the blood of the splenic veins presents the largest proportion of corpuscles, and the pro- 

 portion is smallest in the blood of the hepatic veins. These results favor the idea 

 that the red corpuscles are formed, to a certain extent, in the spleen, and that some 

 are destroyed in the liver ; but farther observations are necessary to render this view 

 certain. 



FIG. 4. Artificial capillary, filled with a sanguin- 

 eous mixture, seen under a quadrilateral mi- 

 crometer. (Malassez.) 



Post-mortem Changes in the Blood- 

 Corpuscles. In examining the fresh blood 

 under the microscope, after the specimen 

 has been under observation a short time, 

 the corpuscles assume a peculiar appear- 

 ance, from the development, on their sur- 

 face, of very minute, rounded projections, 

 like the granules of a raspberry. A little 

 later, when they have become partly de- 

 siccated, they present a shrunken appear- 

 ance, and their edges are more or less ser- 

 rated. Under these conditions, their orig- 

 inal form may be restored by adding to 

 the specimen a liquid of about the den- 

 sity of the serum. When they have been 

 completely dried, as in blood spilled upon 

 clothing or on a floor, months or even 

 years after, they can be made to assume 

 their characteristic form by carefully moist- 

 ening them with an appropriate liquid. This property is taken advantage of in exam- 

 inations of old spots supposed to be blood ; and, if the manipulations be carefully con- 

 ducted, the corpuscles may be recognized without difficulty by the microscope. 



If pure water be added to a specimen of blood under the microscope, the corpuscles 



FIG. 5. Human blood-corpuscles, showing post-mortem 

 alterations. 



