STAGES THROUGH WHICH THE CORPUSCLES PASS. 131 



These are to enumerate them by the terms adopted by Kolliker, and to 

 place them in the probable order of their development 1. colourless 

 nucleated corpuscles (fig. 25 A) ; 2. coloured nucleated corpuscles (B and 

 0) ; and 3. coloured non-nucleated corpuscles. Varieties in size, form, re- 

 lative numbers, and shades of colour, are observed in these corpuscles, 



Fig. 25,* 



itlt 



such as might be expected from the circumstance that they are probably 

 only different transitional stages of development of one kind of corpuscle, 

 and that bodies in all the intermediate states of this transition are com- 

 monly met with in the same sample of blood. Without describing these 

 varieties, which may be found detailed at length by Mr. Wharton Jones, 

 and by Kolliker with whose descriptions the observations of the writer 

 for the most part agree it will be sufficient to observe here that very 

 little doubt now remains of the correctness of the opinion that the first 

 variety, namely, the pale or colourless nucleated corpuscles (which, ac- 

 cording to Kolliker, are developed in the liver) constitute an early stage 

 in the development of the perfect red corpuscles, and that they are gra- 

 dually transformed, first into the nucleated coloured corpuscles, by as- 

 suming colouring matter, and then into the non-nucleated coloured ones, 

 by losing their nucleus and becoming flattened. 



The mode in which the nucleus disappears is not clearly determined. 

 Mr. Wharton Jones is of opinion that the nucleus escapes from the 

 cell, and becoming coloured, constitutes the ordinary red non-nucleated 

 corpuscle of mammalian blood. The principal circumstance which he 

 urges in favour of this view is, that, at least in the adult animal, there is an 

 almost exact correspondence in size between the nucleus of the nucleated 

 blood-cell and the non-nucleated red corpuscle ; and that in those animals 

 which have small red corpuscles, as the goat, the nucleus of the nucleated 

 cell also is small, whilst in those which have large red corpuscles, as the 

 elephant, the nucleus also is large. 



* Fig. 25. Blood corpuscles from a three months' human embryo, magnif. 300 diams. 

 After Kolliker. A. Nucleated colourless corpuscles from the blood of the liver, a, a large 

 nucleated corpuscle with a clear fluid and granules in its interior ; b, a smaller one from 

 which the granules have disappeared ; c, a pale double-nucleated corpuscle with granules ; 

 rf, a double-nucleated one slightly coloured ; e, a single-nucleated, slightly coloured corpuscle, 

 from which the granules have disappeared. B. Slightly coloured nucleated blood- corpuscles 

 from the liver ; a, with two ; 6, with one ; c, with three nuclei, c. Dark-coloured 

 nucleated blood-corpuscles from the aorta ; a, a large one, with a slight depression ; I, 

 a smaller one ; c, one viewed laterally ; d, a smaller one with a constricted nucleus. 



