238 TEXT-BOOK OF PHYSIOLOGY. 



nected with either diet or mode of life, but rather with diminished atmos- 

 pheric, if not oxygen, pressure. On returning to sea-level there is a gradual 

 reduction, without any apparent destruction of the corpuscles, to their normal 

 number. The reason for these variations is not clear. 



The method of counting corpuscles introduced by Vierordt and Welcker 

 has been modified by different observers, and especially by Thoma. On 

 account of the great number of corpuscles in i cubic millimeter of blood, it 

 becomes necessary for purposes of enumeration that the blood be diluted a 

 definite number of times and that the diluted mixture be placed in a counting 

 chamber possessing a definite capacity. By means of the pipette or melang- 

 eur of Potain and the counting chamber of Thoma both these objects are 

 attained. 



The pipette consists of a capillary tube (Fig. 101) provided with an enlarge- 

 ment containing a freely movable small glass ball, E. One end of the tube^S, 

 is pointed, while to the other end is attached a rubber tube, G, for the purpose 

 of facilitating the introduction of the blood and the diluting fluid. The capillary 

 tube, which is accurately calibrated, carries marks, 0.5, i, 101, which signify that 



FIG. 101. HEMOCYTOMETER. a, Surface; b, section view; c, squares on the surface of B magnified- 

 M, G, S, mouth piece, rubber tube and pipette. 



if the tube be filled with blood up to the mark i and the diluting fluid be 

 sucked into the tube up to the mark 101, the blood will be diluted 100 times. 

 If the blood be sucked up to the mark 0.5 and the diluting fluid to 101, then the 

 blood will be diluted 200 times. In using the pipette the point is introduced 

 into a drop of blood derived from a small wound in the skin of the lobe of the 

 ear or finger and sucked into the tube by introducing the end, M, of the rubber 

 tube into the mouth. The tube is then quickly inserted into a solution which 

 will preserve the shape and size of the corpuscles, such as Gowers's sodium sulphate 

 solution, sp. gr. 1.025, or a 3 per cent, sodium chlorid solution, 1 and the fluid 

 1 Various solutions have been devised for diluting blood, any one of which may be employed, e.g.: 

 Hayem's Fluid: Toisson's Fluid: 



Hydrarg. bichlor o . 5 gm. 



Sodii sulphat 5 .o gm. 



Sodii chlorid 2.0 gm. 



Aquae destillat 200 .o gm. 



Aquae destillat 160.00 parts. 



Glycerinae 30 .00 parts 



Sodii sulphat 8 .00 parts. 



Sodii chlorid, i .00 part. 



Methyl- violet, o .025 part. 



Gower's Fluid: 



Sodii sulphat ................................................. gr. 



Acid, acetic ................................................... 5 j 



Aquae dest .............................................. q. s. ad 5i 



104 



