THE BLOOD. 81 



and then by the lengthening out and attenuation of the connection, and 

 finally by its rupture, two corpuscles result. The nuclei have previously 

 undergone, division. The cells so formed are said to be remarkably active 

 in their movements. Thus we see that the rounded form which the 

 colorless corpuscles present in ordinary microscopic specimens must be 

 looked upon as the shape natural to a dead corpuscle or to one whose 

 vitality is dormant rather than as the shape proper to one living and 

 active. 



Action of re-agents upon the colorless corpuscles. Feeding the 

 corpuscles. If some fine pigment granules, e.g., powdered vermilion, 

 be added to a fluid containing colorless blood-corpuscles, on a glass slide, 

 these will be observed, under the microscope, to take up the pigment. In 

 some cases colorless corpuscles have been seen with fragments of colored 

 ones thus embedded in their substance. This property of the colorless 

 corpuscles is especially interesting as helping still further to connect them 

 with the lowest forms of animal life, and to connect both with the organ- 

 ized cells of which the higher animals are composed. 



The property which the colorless corpuscles possess of passing through 

 the walls of the blood-vessels will be described later on. 



Enumeration of the Red and White Corpuscles. Several 

 methods are employed for counting the blood-corpuscles, most of them 

 depending upon the same principle, i.e., the dilution of a minute volume 

 of blood with a given volume of a colorless solution similar in specific 

 gravity to blood serum, so that the size and shape of the corpuscles is 

 altered as little as possible. A minute quantity of the well-mixed solu- 

 tion is then taken, examined under the microscope, either in a flattened 

 capillary tube (Malassez) or in a cell (Hayem & Nachet, Gowers) of 

 known capacity, and the number of corpuscles in a measured length of 

 the tube, or in a given area of the cell is counted. The length of the 

 tube and the area of the cell are ascertained by means of a micrometer 

 scale in the microscope ocular; or in the case of Gowers' modification, by 

 the division of the cell area into squares of known size. Having ascer- 

 tained the number of corpuscles in the diluted blood, it is easy to find 

 out the number in a given volume of normal blood. Gowers' modifica- 

 tion of Hayem & Cachet's instrument, called by him "Hcvmacytometer," 

 appears to be the most convenient form of instrument for counting the 

 corpuscles, and as such will alone be described (Fig. 79). It consists of 

 a small pipette (A), which, when filled up to a mark on its stem,,, holds 

 995 cubic millimetres. It is furnished with an india-rubber tube and 

 glass mouth-piece to facilitate filling and emptying; a capillary tube (B) 

 marked to hold 5 cubic millimetres, and also furnished with an india- 

 rubber tube and mouthpiece; a small glass jar (D) in which the dilution 

 of the blood is performed; a glass stirrer (E) for mixing the blood 

 thoroughly, (F) a needle, the length of which can be regulated by a, 

 VOL. I. 6. 



