ORIGIN OF RED BLOOD-CORPUSCLES. 339 
They possess an extremely marked tendency to run together, 
either with one another, with the leucocytes, or with the 
hgematids, even in the blood in circulation when under ab- 
normal conditions. 
The proportional number of the globulets varies con- 
siderably according to circumstances. They are exceedingly 
easy to study in very young cats ; speaking generally, they 
are not easily seen in animals whose blood is being repaired. 
Le^igth of duration and fate of the heematids . — It is quite 
clear that parts of our organism which are as much exposed to 
accidental losses as are the elements of the blood, and even 
to periodic losses which accompany certain functions, ought 
to be always undergoing a regeneration, this regeneration 
only becoming more or less active according to circum- 
stances. 
A consequence of this constant regeneration is that, 
although one must consider some element in the body 
as perennial, e, g, nerve cells, it is hardly possible to 
think so of either hsematids or leucocytes. The elements 
of the blood have therefore a short existence, how short we 
know not; various things point to its being only a few 
weeks, or at most a few months. 
If mammal’s blood is transfused into bird’s blood, the 
haematids are found unaltered at the end of fifteen or 
twenty days. 
Brown-Sequard found this to be the case, and I have 
since repeated the experiments, using the dog and pigeon. 
On the other hand, the haematid of birds placed in a mammal 
are not to be found after a few^ hours only ; this may simply 
be attributed to the much greater diameter of the haematid of 
the bird. These latter seem to be almost immediately killed 
and destroyed by the state of the new medium in which 
they are placed. 
If it is difficult to ascertain the absolute age of a haematid, 
it seems easier to determine their relative age. 
As a rule with mammal’s haematids as well as with those 
of oviparous animals, the nearer they are to their period of 
decline and disappearance the more coloured and refractive 
are they. There is no doubt that the haematids end by 
becoming dissolved in the serum. They diminish in volume, 
and finally take a more or less regular spherical form. They 
answer in this state to the description of elements found in 
this hypothesis a more or less distant analogy, between this phenomenon 
and the formation of the directive corpuscles ; a common character being 
the regular segmentation of the nucleus of the leucocytes into four and the 
regular segmentation of the vitellus, &c. 
