42 BLOOD. 



This, perhaps, may be most conveniently done by the method generally known 

 as that of Growers (Hsemacytometer) [Fig. 8 j, improved by Malassez. A glass 

 slide, in a metal frame, is ruled into minute rectangles, e. g. \ mm. by i mm., so 

 as to give a convenient area of ^V of a square mm. Three small screws in the frame 

 permit a coverslip to be brought to a fixed distance, e. g. \ mm., from the surface 

 of the slide. The blood having been diluted, e. g. to 100 times its volume, a small 

 quantity of the diluted (and thoroughly mixed) blood, sufficient to occupy fully the 

 space between the coverslip and the glass slide when the former is brought to its 

 proper position, is placed on the slide, and the coverslip brought down. The 

 volume of diluted blood now lying over each of the rectangles will be T ^o (?\yX) 

 of a cubic mm.; and if, when the corpuscles have subsided, the number of cor- 

 puscles lying within a rectangle be counted, the result will give the number of 

 corpuscles previously distributed through y^ of a cubic mm. of the diluted 

 blood. This multiplied by 100 will give the number of corpuscles in 1 cubic 

 mm. of the diluted blood, and again multiplied by 100 the number in 1 cubic 

 mm. of the entire blood. It is advisable to count the number of corpuscles in 

 several of the rectangles, and to take the average. For the convenience of count- 

 ing, each rectangle is subdivided into a number of very small squares, e. g. into 20, 

 each with a side of -$ mm., and so an area of ^^ of a square mm. 



Since the actual number of red corpuscles in a specimen of blood (which 

 may be taken as a sample of the whole blood) is sometimes more, sometimes 

 less, it is obvious that either red corpuscles may be temporarily withdrawn 

 from and returned to the general blood current, or that certain red corpuscles 

 are, after a while, made away with, and that new ones take their place. We 

 have no satisfactory evidence of the former being the case in normal condi- 

 tions, whereas we have evidence that old corpuscles do die and that new 

 ones are born. 



26. The red corpuscles, we have already said, are continually engaged 

 in carrying oxygen, by means of their haemoglobin, from the lungs to the 

 tissues ; they load themselves with oxygen at the lungs and unload at the 

 tissues. It is extremely unlikely that this act should be repeated indefinitely 

 without leading to changes which may be familiarly described as wear and 

 tear, and which would ultimately lead to the death of the corpuscles. 



We shall have to state later on that the liver discharges into the alimen- 

 tary canal, as a constituent of bile, a considerable quantity of a pigment 

 known as bilirubin, and that this substance has remarkable relations with, 

 and, indeed, may be regarded as a derivative of hcematin, which, as we have 

 seen ( 24), is a product of the decomposition of haemoglobin. It appears 

 probable, in fact, that the bilirubin of bile (and this as we shall see is the 

 chief biliary pigment, and the source of the other biliary pigments) is not 

 formed wholly anew in the body, but is manufactured in some way or other 

 out of haematin derived from haemoglobin. This must entail a daily con- 

 sumption of a considerable quantity of haemoglobin, and since we know no 

 other source of haemoglobin besides the red corpuscles, and have no evidence 

 of red corpuscles continuing to exist after having lost their haemoglobin, 

 must, therefore, entail a daily destruction of many red corpuscles. 



Even in health, then, a number of red corpuscles must be continually 

 disappearing ; and in disease the rapid and great diminution which may 

 take place in the number of red corpuscles shows that large destruction 

 may occur. 



We cannot at present accurately trace out the steps of this disappearance 

 of red corpuscles. In the spleen pulp, red corpuscles have been seen in 

 various stages of disorganization, some of them lying within the substance 

 of large colorless corpuscles, and as it were being eaten by them. There is 

 also evidence that destruction takes place in the liver itself, and, indeed, 

 elsewhere. But the subject has not yet been adequately worked out. 



27. This destruction of red corpuscles necessitates the birth of new 



