1106 
DR. H. WATNEY OH THE MINUTE ANATOMY OF THE THYMUS. 
even into a succession of glands, where it is possible that these colourless cells may be 
changed. It is therefore difficult to form any very certain conclusions as to the 
functions of these colourless cells, although probably they form one source of the 
colourless blood corpuscles. 
The difference in size between the thymic corpuscles and the coloured blood cor¬ 
puscles is seen to be very great in some classes of Vertebrates, and we have no reason 
to believe that the one are ever immediately transformed into the other (see Plate 92, 
figs. 72, 73, 74, and 75, be and The). 
There is one fact which presents considerable difficulties— -i.e., that the blood of the 
foetus and of the newly-born animal contains a considerably larger proportion of coloured 
to colourless blood corpuscles than is the case in the blood of adults. This was first 
noticed by Denis (95), and then by Panum (96), and yet the thymus is certainly more 
active during foetal life and during the first years of growth than it can be during adult 
life, when it is composed in a great measure of connective-tissue. 
In considering the uses of the cells containing haemoglobin, it has been stated above 
that we find large colourless cells containing masses in shape exactly identical with, 
though in size generally smaller than, the coloured blood corpuscles ; and this is true, 
not only in all Mammals with circular corpuscles (see Plate 86, fig. 21), but in the Camel 
(see Plate 92, fig. 77, d), and also in the Bird, Reptile, and Pish. It is considered by 
Kolliker (97) and most authors that these cells, as found in the spleen where they 
have long been known, are large colourless cells which have absorbed coloured blood 
corpuscles; but there are very great difficulties in holding that view-—first, because we 
have found these cells in the lymphatics, in the blood in two cases of leucocythemia, in 
the thymus, the lymphatic glands, and the medulla of young bone,* and in no one of 
these situations have we any knowledge of any destruction of coloured blood corpuscles 
taking place ; and secondly, because if such a destruction were taking place, it would 
seem somewhat difficult to understand how these contained masses of haemoglobin, in 
undergoing solution, retain their form. And it seems to me that the older view of 
Gerlach (106) and Schaffner (107) as to the origin of coloured blood corpuscles, is 
quite as worthy of support as any other, in the present state of our knowledge ; and 
more especially so when we consider that the coloured blood corpuscles in the embryo 
in early life are formed from large colourless cells, as seen by Klein (108), Balfour (109), 
and others, in the Chick, and from connective tissue cells or network, as seen by 
Schafer (110), Wissozky (111), and Ranvier (112) in young Mammals. 
* Further, in two cases of pernicious anaemia, which were examined, the medulla of the long hones was 
found to contain large cells enclosing spherules and masses of haemoglobin, some of them enclosing masses 
exactly resembling coloured blood corpuscles. Ponfick (98), Fede (99), Cohnheim (100), Osler and 
Gardner (101), Litten and Orth (102), and Riess (103) have described the occurrence of cells containing 
blood corpuscles in the medulla of patients who had died from pernicious anaemia, and Neumann (104), 
Bizzozero (105), Ponfick (98), Litten and Orth (102) have seen them in the medulla after typhoid 
fever or other diseases. 
