ORIGIN OF RED BLOOD-CORPUSCLES. 
335 
and gradually become transformed into red corpuscles 
(h^matids) ; he gives a very accurate description of these 
hsematoblasts. Repeated experiments on birds have afforded 
me precisely the same results. Neither M. Vulpian nor 
M. Hayem have put forward any opinion as to the origin of 
these haematoblasts. I have stated before that they are 
derived from nuclei of origin. But whence do these latter 
come ? Do they all come from the broken and scattered 
nuclei of leucocytes which have finished their existence? 
Fishes have no lymphatic glands. Some animals have 
no spleen. Is it possible to admit that the nuclei of origin 
originate, in this latter case, from the cells lining the w^alls 
of the lymphatic cavities, and that in the other oviparous 
animals the spleen, if not the exclusive place of their pro- 
duction, at any rate plays an important part in it ? In fact, 
I have shown that among Selachians the spleen is partly 
formed of elements which are identical with these nuclei of 
origin, and which, detaching themselves one by one, fall into 
the network forming the tissue of the organ, and are carried 
away by the blood. It must be admitted that the spleen 
plays, among oviparous animals, a part which it plays, per- 
haps, among the mammals, and which corresponds, at all 
events, to that of the lymphatic glands of the latter group. 
Lastly, it results from certain experiments which I per- 
formed some time ago upon birds. Amphibia, and fishes, that 
the removal of the spleen only hinders the reparation of the 
blood after death, and that either the nuclei of origin are 
continually originating from the walls of the lymphatics, or 
that the leucocytes of the blood are sufficient for this 
multiplication. 
Leucocytes of Semmer . — When the blood of an oviparous 
animal, and often when that of a mammal, is examined, it 
is possible to find certain elements, the nature of which has 
been for a long time misunderstood. 
I thought I had been the first to describe them in the 
blood of Selachians (Soc. de Biologie, Nov. 7). I have since 
remembered that attention had already been drawn to them 
in a special manner among mammals by a pupil of Alexander 
Schmidt, in a paper written at Dorpat. I propose to call 
them, after the author of this paper, leucocytes of 
Semmer. 
Even if their existence was known, their fundamental 
structure had escaped all previous observers ; they may be 
regarded as leucocytes (they are the same size, possess 
amoeboid powers, &c.), in the body of which haemoglobin is 
formed. The latter is in large granules, generally measuring 
