ORIGIN OF RED BLOOD-CORPUSCLES. 
343 
tissue of the nodules^ which has nothing whatever to do 
with haematogenesis^ has given rise. 
The Spleen . — The older observers, by experiments which 
I have repeated, proved beyond a doubt that the spleen was 
not essential in the regeneration of the blood after extensive 
haemorrhage. I have already briefly described the struc- 
ture of the tissue of the spleen. As T said, it is extremely 
probable that a large number of the haematids are normally 
arrested in it when they have lost their elasticity, which they 
do as they grow old, on account of the large amount of 
haemoglobin then present. These old haematids, thus re- 
tained in the meshes of the splenic tissue, certainly help to 
give it its colour, which it possesses even when there is very 
little blood in it.^ 
The fact that the serum found in the splenic vein 
appears to be more yellow than that found in other vessels 
(G. E. Rindfleisch), might perhaps be explained by this 
breaking up of the old haematids, which are arrested in the 
parenchymatous tissue of the spleen. 
Those who have attributed to the spleen a definite 
haematogenetic function, ought, at the same time, to re- 
member that haematogenesis is no less active in mammals 
from which the spleen has been removed ; they have gone 
further, and supposed that the spleen was helped by the 
mesenteric glands, and, indeed, even by the subperitoneal 
tissue ! At least, it ought to be proved in this case that the 
glands and the cellular tissue have taken on the totally 
(lifierent histological structure of the spleen-parenchyma ; 
and the stages of such a wonderful transformation, which 
would be one of the most eurious known to anatomists, 
ought to be pointed out ! On the other hand, it would be a 
senseless physiology which ascribed to two organs, of such 
essentially different structure and texture as these, the 
same function. It is really astonishing that biologists 
have accepted this singular idea of a vicarious action, 
as it has been called, on the part of certain organs which 
are supposed to take on, for the time being, the functions 
^ Probably the Malpighian corpuscles ought not to be looked upon as 
special structures, but simply as regions where the splenic tissue, more or 
less accidentally, has become impermeable to the blood which passes through 
the organ. In teleostian fishes these impermeable regions are not isolated, 
but form a thick net-work in the organ ; moreover, in Amphibia there is a 
development of certain cells of the spleen, which recalls (at least, so far as 
one can judge without having specially studied it) the development of those 
cells, which 1 shall describe further on, in the marrow of the bones of 
mammals. 
VOL. XX. NEW SER, 
Z 
