30 ORGANISED FLUIDS. 



graphers, aided by the application of a variety of re-agents, 

 have failed, utterly, in detecting the presence of a similar 

 structure in the blood globule of the human subject in 

 particular, and of mammalia in general. I therefore do not 

 hesitate to join my opinion to that of those observers who 

 deny the existence of a nucleus in the blood discs of man 

 and mammalia.* 



The appearance of a nucleus is, indeed, occasionally pre- 

 sented; but this appearance has been wrongly interpreted. 

 An internal small ring, under favourable circumstances, may 

 be seen in the centre of each blood corpuscle : this ring 

 is occasioned by the central depression, the outer margin of 

 which it describes ; and it was the observance of it that gave 

 to Delia Torre the erroneous impression, that each globule 

 had a central perforation, and therefore was of an annular 

 form ; and further, probably induced Dr. Martin Barry to 

 describe it as a fibre. 



The very existence, on both surfaces of the blood disc, of 

 a deep central depression, together with its little thickness, 

 almost preclude the possibility of the presence of a nucleus. 



An endeavour to account for the absence of a nucleus in 

 the blood corpuscle of the human adult has been made by 

 supposing that it does really exist in the blood of the embryo. 

 The answer to this supposition is, that no nucleus is to be 

 found in embryonic blood, and that if it were, it would be no 

 reason why the nucleus should not also be met with in the 

 blood of the adult, seeing that the blood disc is not a perma- 

 nent structure, as an eye or a limb, but one which is per- 

 petually subject to destruction and renewal. 



Having then arrived at the conclusion that no nucleus 

 exists in the blood corpuscle of man, \ve have now to ask 

 ourselves the question, what, then, is really the constitution of 

 the red blood globule ? 



* Amongst those who have asserted their belief in the presence of a 

 nucleus, may be mentioned Hewson, Miiller, Gerber, Mandl, Barry, 

 Wagner, Rees, Lane, and Addison; and of those who have held a contrary 

 opinion, Majendie, Hodgkiu, Liston, Young, Quekett, Gulliver, Lain- 

 botte, Owen, and Donne. 



