ORIGIN OF RED BLOOD-CORPUSCLES. 
333 
present here in an order which, if not the most logical, 
is probably the best for a rapid resume. 
It is curious that most of those who have worked at 
haematogenesis have been led to recognise from the first the 
inaccuracy and incompleteness of the descriptions which 
have been given, up to the present, of the formed elements 
of the blood. One would have thought that objects so easily 
examined would have been well known. Nothing of the 
sort. Certain elements, of perhaps capital importance, have 
been completely neglected, others badly described, while as 
to the origin of all, one is reduced to the vaguest hypotheses. 
In short, our first want seems to be to complete here, as 
well for the oviparous vertebrates as for the mammals, such 
descriptions as are found in the recognised text-books, and 
even in a whole host of special memoirs on the subject, 
which have been recently published. 
Blood of Oviparous Animals . — Among all oviparous 
animals — those which are warm-blooded — birds, as well as 
those which are cold-blooded — reptiles, amphibians, and 
fishes — the method of formation in the adult seems to be 
the same. Among embryos it evidently differs according 
as the embryo has or has not an umbilical vesicle. 
In the adult the question of the formation of the elements of 
the blood seemed actually settled. The size of the elements 
in Amphibia naturally induces histologists to study these 
first. I took the newt as the basis of my investigations. 
There are in the blood of the newt certain elements not 
corpuscles, which have hitherto all been included under the 
general term leucocytes. These I have called, for the sake 
of clearness, '^nuclei of origin;” however, by no means in- 
sisting upon this term. These nuclei of origin” are 
spherical, and about t^-o twit diameter. 
They are enveloped by a very thin layer of protoplasm, of 
equal thickness all round the nucleus. I will return pre- 
sently to the origin of these elements ; it is their further 
development which concerns me at present. This develop- 
ment may take place in two different methods : 
a. The nucleus of origin” enlarges and segments, and 
the protoplasm becomes proportionally increased in bulk ; 
in short, the nucleus becomes a leucocyte with numerous 
nuclei. After this stage, when it may be called adult, it 
must necessarily disappear; the protoplasm disintegrates 
in the serum, setting free the nuclei, which are nothing else 
than nuclei of origin about to recommence a new cycle. 
This appears to be the normal state of things. 
b. The nucleus of origin may be destined to become i\ 
