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HANDBOOK OF PHYSIOLOGY. 



form of masses or chains of globular material. Chemically they contain 

 a micleo-proteid, and it is supposed that they take part in the phenom- 

 enon of coagulation. 



Healthy bacillus .- 



Healthy bacillus 



Healthy bacillus 



Partially digested bacillus 



Partially digested leucocyte 



Nuclei vacuolated 



. Nucleus 



Bacillus in leucocyte 

 =\. Partially digested leucocyte 



Foreign matter 



Foreign matter 



Leucocytes - 



Particles of foreign matter 



Particles of foreign matter 



Particles of foreign matter 



Fig. 129. Macrophages containing bacilli and other structures supposed to be undergoing digestion. 



(Ruffer.) 



Enumeration of the blood-corpuscles. Several methods are employed for 

 counting the blood -corpuscles, most of them depending upon the same princi- 

 ple, i.e., the dilution of a minute volume of blood with a 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 & 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 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 instru- 

 ment, called by him Hcemacytometer, consists of a small pipette (A) , which, 

 when filled up to a mark on its stem, holds 995 cubic millimetres. It is fur- 

 nished 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 (E) for mixing 

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

 screw j a brass stage plate (G) carrying a glass slide, on which is a cell one- 



