CHAP. i.J BLOOD. 31 



the analysis of the small quantities at disposal, in its chemical 

 composition, is identical with bilirubin, the primary pigment of 

 bile. Moreover, according to some observers the injection of 

 haemoglobin, or of dissolved red corpuscles, into the vessels of a 

 living animal, gives rise to a large amount of bile-pigment in the 

 urine, and at the same time increases enormously the relative 

 quantity of bilirubin in the bile. Thus though no one has yet 

 succeeded in producing bilirubin artificially from haemoglobin, andj 

 the actual identity of the two cannot as yet perhaps be regarded' 

 as settled, facts, and especially perhaps the presence of haem 

 globin, in the serum of the splenic vein, and its disappearance aft 

 the blood has passed through the liver, point very strongly to th 

 view that the red corpuscles are used up to supply bile-pigment. 



Our knowledge of urinary pigments is so imperfect that little 

 can be said as to their relation to haemoglobin. We cannot at 

 present definitely trace the normal urinary pigment back to 

 haemoglobin, however probable such a source may seem. 



As regards the white corpuscles of the blood, using this 

 term without prejudice or as to the question whether or no 

 there be more than one distinct kind, these as we have seen 

 also come and go. 



The fact that in the lymphatic glands, and other adenoid 

 structures, corpuscles, similar to if not identical with white blood- 

 corpuscles, are to be seen of very various sizes, many with double 

 nuclei and some indeed actually dividing into two corpuscles, 

 suggests that these organs are the birth-places of the white 

 corpuscles. The lymph is continually pouring into the blood a 

 crowd of white corpuscles, which, since they for the most part 

 make their appearance in the lymph-vessels after the latter have 

 traversed the lymphatic glands, probably take origin from those 

 bodies. 



At the same time it is open for us to suppose that any 

 proliferating tissue may give rise to new corpuscles; and Klein 

 states that he has seen them budded off from the reticulum of the 

 spleen. The white corpuscles have also been observed to divide 1 . 



We may conclude therefore that the white corpuscles probably! 

 arise, by division chiefly, from the corpuscles of adenoid tissue, but 

 that other sources may exist. 



While we are able to attribute to the numerous red corpuscles 

 an important respiratory function, we are at present at all 

 events unaware of any special work carried on by the scantier 

 white corpuscles while they are being hurried along in the blood 

 current. As far as our present knowledge goes they seem to tarry 

 in the blood only on their way either to be broken up or to pass 

 into the tissues. 



We have already referred to the probable view that it is not the 

 ordinary white corpuscle but a special kind of corpuscle which is 

 1 Klein, Hdb. Phys. Lab., p. 8. 



