VI.] 



THE COLOURED BLOOD CORPUSCLES. 



45 



(e.) "Wash the instrument, and in cleaning the cell do this witli 

 a stream of distilled water from a wash-bottle. Take care not to 

 brush the cell with anything rougher than a camel's-hair pencil, to 

 avoid injuring the lines. 



Each square has an area of y^ of a square mm., so that lo 

 squares have an area of y^^ of a square mm. As the cell is ^ mm. 

 deep, the volume of blood in lo squares is yg- x^ = -^^ c.mm. On 

 counting the number of corpuscles in lo squares, and multiplying 

 by 50, this will give the number in i c.mm, of the diluted blood. 

 On multiplying this by ^~j w'e get the number in i c.mm. before 

 dilution. Thus we arrive at the reason why we multiply the 

 number in 10 squares by 10,000 to get the number of corpuscles in 

 I c.mm. of blood. 



HAEMOGLOBIN AND ITS DERIVATIVES. 



^y 



c 



? 



3. Preparation of Haemoglobin Crystals, (C,,oo^^9GoNi54C>i79SFe) 

 (a.) Rat's Blood.— Place a drop of detibrinated rat's blood on a 



slide, add three or four drops of water, 



mix, and cover with a cover-glass. Ex- 

 amine with a microscope ; after a few 



minutes small crystals of oxy-hiemo- 



globin will begin to form, especially 



at the edges of the preparation, and 



gradually grow larger in the form of 



thin rhombic plates arranged singly or 



in groups (fig. 21). 



{h.) Guinea-Pig's Blood.— Treat the 



blood of a guinea-pig as directed for 



the blood of a rat. Tetrahedral crystals 



are obtained. Mount some defibrinated 



blood in Canada balsam. Crystals 



form. 



/ \ T\ 1 -ni J _, r 1 n-, • . 1 FiQ- 21.— 5-8emoglobiii Crystals 



(c.) Dog's Blood.— To 15 cc. of defibrinated from Rat's Blood, 



dog's blood add, drop by drop, i oc. or 



so of ether, shaking the tube after each addition of ether. By this means 

 tlie blood is rendered lakj/, a condition which is recognised by incHning 

 the tube, and observing that the film of blood left on it, on bringing the 

 tube to the vertical again, is transparent. Add no more ether, but })lace the 

 tube in a freezing mixture of ice and salt ; as the temperature falls, crystals 

 of h.nemoglobin separate. If the crystals do not separate at once, keep the 

 tube in the freezing mixture for one or two days. Examine the crystals 

 microscopically. Arthus finds that dog's blood, containing i per cent, of 

 sodic fluoride, after standing for several days, according to the surrounding 

 temperature, deposits crystals of Hb. 



