62 



PRACTICAL HISTOLOGY. 



Cohnheim proved the practical importance of feeding the white blood 

 corpuscles with these pigments, by injecting for several days in succes- 

 sion 2 or 3CC of water with fine particles of aniline blue, into a sub- 

 cutaneous lymph sac of the frog. The lymph corpuscles enveloped the 

 blue granules and entered the circulation. After some days he in- 

 duced inflammation of the cornea, and found among the pus-cells at the 

 seat of irritation, some containing the blue granules, proving that they 

 had emigrated from the blood-vessels into the comeal tissue. 



830. Enumeration of the Blood Corpuscles. Malassez 

 and Potain have devised a method for estimating the number of coloured 

 corpuscles in a given quantity of blood (Archives de Physiologic, 1874, 

 p. 32), a matter of much importance both in physio- 

 logy and pathology. 



The blood is diluted with an artificial serum in 

 order to prevent coagulation, and to facilitate the 

 counting of the corpuscles. The artificial serum 



fl consists of I vol. watery solution of gum arabic, 

 / having a Sp. G. of 1020, 3 vols. watery solution of 

 / equal parts of sodium sulphate and sodium chloride, 

 having a Sp. G. of 1020. The mixture of the 

 blood with the above serum may be made in an 

 ordinary CC measure; but if the quantity of blood 

 be small, the pipette shown in Fig. 41 is essential. 

 This is a glass pipette with a capillary tube, and a 

 bulb containing a glass bead for mixing the blood 

 and serum. An elastic tube, about a foot in length, 

 is attached to one extremity. In estimating the 

 number of coloured corpuscles in human blood, the 

 finger is pricked, and a large drop of blood ex- 

 pressed, the elastic tube is placed in the mouth, the 

 pointed end of the pipette in the drop of blood, and 

 the fluid is sucked into the tube until it exactly 

 reaches the line marked I. The point of the pipette 

 is then placed in the serum, and the aspiration con- 

 tinued until the fluid exactly reach the line c. 

 During the entrance of the serum, the pipette is 

 shaken, so that the glass bead may cause its thorough 

 admixture with the blood. The instrument is so 

 graduated that the cavity of the pipette below the 

 line i contains exactly T |^ part of the cavity of the 

 bulb from the line I to the line c. The mixture of 

 blood and serum, therefore, contains one per cent 

 of blood. In cases where the blood corpuscles are 

 very numerous, it is advantageous to have only half a per cent of blood 

 in the mixture. In such a case the aspiration of the blood into the 

 pipette is arrested when the line marked ^ is reached, and the serum is 

 added as before. One must be careful to remember that after the 

 mixture is made, the fluid in the long stem of the pipette is merely 

 serum, and must be expelled as useless. 



FIG. 41. Pipette for 

 diluting blood with 

 artificial serum. 

 (After Malassez.] 



