62 



PRACTICAL PHYSIOLOGY. 



[VII 



(ft.) Prick the finger as in 7 with the instrument supplied for the purpose. 

 Fill the short automatic capillary pipette tube with blood. Its capacity is 

 6.5 c.mm. In filling the tube, hold it horizontally. See that no blood 

 adheres to the surface of the tube. This can be done by having the pipette 

 slightly greasy on the outer surface. 



(c.) Dissolve the blood obtained in (&.) in the water of the blood-compart- 

 ment (), washing out every trace of blood from the pipette. Mix the blood 

 and water thoroughly. Clean the pipette. Then fill the blood compartment 

 exactly to the surface with distilled water, seeing that its surface also is per- 

 fectly level. 



(d.) Arrange a candle in front of the reflector (S) which is white, and with 

 a smooth matt surface made of plaster-of- Paris so as to throw a beam of light 

 vertically through both compartments. Look down vertically upon both 

 compartments, and move the wedge of glass by the milled head (T) until the 

 colour in the two compartments is identical. Read off the scale, which is so 

 constructed as to give the percentage of hsemoglobin. 



9. Bizzozero's Chromo-Cytometer. The chief part of the instrument con- 

 sists of two tubes (fig. 37, ab, cd\ working one within the other, and closed 

 at the same end by glass discs, while the other ends are open. The one tube 



can be completely screwed into 

 the other, so that both glasses 

 touch. Connected with the outer 

 tube is a small open reservoir (>), 

 from which fluid can pass into 

 the variable space between the 

 two glass plates at the ends of 

 the tubes. By rotating the inner 

 tube, the space between the two 

 glass plates can be increased or 

 diminished, on the principle of 

 Hermann's ha^matoscope, and 

 the screw is so graduated as to 

 indicate the distance between 

 the two plates, i.e., the thick - 



_ ness of fluid between them. Each 



^ complete turn of the screw = 0.5 



J mm., and the subdivisions on it 



f are so marked 25 to one turn 



(index fig. 37 erf) that each 



subdivision of the index = _i5 



= o.O2 mm. When the 



25 

 inner 



Fia. 37. General View of the Chromo-Cytometer. 

 ab and cd. Two tubes, the one fits inside the 

 other ; r. Reservoir communicating with the tube is screwed home and touches 

 space between c and b when cd is screwed into the glass disc in the outer tube, 

 ab ; cr. Milled-head and index scale to the left J/L j + j j. ~ ~ +.u i 

 of it, for the tinted glass ; m. Handle. Jhe index stands at o on the scale 



It the instrument is to be used 



merely as a eytometer, these parts suffice ; but if it is to be used as a chromo- 

 meter, the coloured glass must be used. The instrument is also provided 

 with small glass thimbles with flat bottoms, containing 2 and 4 cc. respectively; 

 a pipette graduated to hold \ and I cc., and another pipette for 10 and 20 

 c.mm., the latter provided with an india-rubber tube, to enable the fluid 

 to be sucked up readily ; a bottle to hold the saline solution, and a glass 

 stirrer. 



Method of Using the Instrument as a Cytometer. i. By means of the 

 pipette place 0*5 cc. in normal saline solution in a glass thimble. 



