346 
PROFESSOR POUCHET. 
marrow is quite immovable and specially fixed in the solid 
substance of the bone. 
Another question arises, if this degeneration were to go on ' 
at the same time in a number of elements bordering upon a 
capillary, the wall which, as we have seen, is formed of a 
single layer of endothelial cells, would break through sooner . 
or later and allow the blood stream to take in these new 
h^ematids while they were yet undeveloped, while a new 
endothelial wall would have to form to cover up the space 
where they had been set free. In other words, would not the 
capillaries of bone be continually undergoing development 
or rather displacement in the medullary tissue ? Nothing in 
such observations relating to this, as I for my part have 
been able to make, furnish any indication of anything of 
the kind taking place, or that the medullary cells while 
undergoing development come into any special relation with 
the capillaries. 
Certain anatomists have thought that the marrow of the 
bones was modified after great hsemorrhage, and when the 
blood is being regenerated. All the experiments — which, 
however, have not been many — that I have made in this 
matter, have not shown this to be the case. 
It must then be admitted, and T think we can go no 
further, that the marrow cells undergo in situ a haemoglobic 
degeneration comparable to that taking place in the hsema- 
tids of birds, and which also takes place in the marrow of 
the bones of birds before it has given place to the air cavi- 
ties. In fact, marrow exists in the bones of reptiles and 
Amphibia, as well as in young birds, and yet no one has 
dreamt of ascribing any haematopoietic function to it. 
Fishes have no marrow in their bones. 
To sum up : — the development of haematids among ovi- 
parous animals and that of the marrow cells are two processes 
which are in all points comparable to one another, just as 
the appearance of granules of haemoglobin in the lymphatic 
gland is comparable to what happens in the leucocytes of 
Semmer. 
It has been attempted to found an argument in favour of 
the haematopoietic function of the marrow on the existence, 
which has been proved from time to time, of cells in the blood, 
with a nucleus and a body containing haemoglobin-cells con- 
sequently analogous to the haematids of birds, only often 
without a regular form. 
It will be sufficient to draw attention to the extraordinary 
rarity of these elements which one hardly finds in one out 
of a liundred preparations. They arc not moreover more 
