76 HANDBOOK OF PHYSIOLOGY. 



Action of reagents 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 imbedded 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 organized 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 blood-corpuscles. Several methods are em- 

 ployed for counting the blood-corpuscles, most of them depending upon 

 the same principle, i.e., the dilution of a minute volume of blood with 

 SL given volume of a colorless solution similar in specific gravity to blood 

 plasma, so that the size and shape of the corpuscles is altered as little as 

 possible. A minute quantity of the well-mixed solution is then taken, 

 examined under the microscope, either in a flattened capillary tube 

 (Malassez) or in a cell (Hayem & Cachet, 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 micro- 

 scope ocular; or in the case of Gowers' modification, by the division of 

 the cell area into squares of known size. Having ascertained the number 

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

 given volume of normal blood. Gowers' modification of Hayem & 

 Nachet's instrument, called by him '* Hcemacytometer," appears to be the 

 most convenient form of instrument for counting the corpuscles, and as 

 such will alone be described (Fig. 76). It consists of a small pipette 

 (A), which, when filled up to a mark on its stem, holds 995 cubic milli- 

 metres. 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 

 mouth-piece; a small glass jar (D) in which the dilution of the blood is 

 performed; a glass stirrer (B) for mixing the blood thoroughly, (F) a 

 needle, the length of which can be regulated by a screw; a brass stage 

 plate (c) carrying a glass slide, on which is a cell one-fifth of a millimetre 

 deep, and the bottom of which is divided into one-tenth millimetre 

 squares. On the top of the cell rests the cover-glass, which is kept in 

 its place by the pressure of two springs proceeding from the stage plate. 

 A standard saline solution of sodium sulphate, or similar salt, of specific 

 gravity 1025, is made, and 995 cubic millimetres are measured by means 

 of the pipette into the glass jar, and with this five cubic millimetres of 

 blood, obtained by pricking the linger with a needle, and measured in the 

 capillary pipette (B), are thoroughly mixed by the glass stirring-rod. A 

 drop of this diluted blood is then placed in the cell and covered with a 

 cover-glass, which is fixed in position by means of the two lateral springs. 

 The preparation is then examined under a microscope with a power of 

 about 400 diameters, and focussed until the lines dividing the cell into 

 .squares are visible. 



