M. Coste on the Formation of Cells. 379 
be taken to study the tissues in the germ itself, and at the time 
of their earliest origin, we can then clearly recognise that their 
structure is for the most part composed, like those of vegetables, 
of cells, which are so much the more easily recognised the less 
their forms are obscured by development. 
Now, from the moment at which it was demonstrated that the 
cell constitutes the base of all the organic tissues, that it is as it 
were the integral molecule, we could not fail to attach the utmost 
value to the discovery of the mechanism of its formation. This 
was, in fact, one of the most curious and most secret phenomena 
im nature which direct observation could unfold; for by this new 
conquest science extended the limits of its dominion so far as to 
observe living matter, still diffuse, commencing to individualize 
itself in one of the most simple forms which organization is ca- 
pable of assuming, that is, in that of a vesicle, utricle or cell. 
The honour of the commencement is due to M. Mirbel. This 
physiologist first investigated the origin of the cell from the 
cambium, and the formation of its walls at the expense of this 
mucilage. In fact, in the large interstices which the vegetable 
utricles leave between them, or even in the cavity of these utri- 
cles, there exists a mucilagimous matter comparable to gum- 
arabic, in which the most perfect instruments cannot recognise 
any trace of visible organization, but which becomes the gene- 
rating element of every organic form. ‘This diffused matter, 
which Grew discovered more than 150 years ago, and the use of 
which he surmised, has been traced by M. Mirbel through the 
principal modifications which it undergoes in certain vegetables, 
and the following exhibits the succession of phenomena through 
which he has seen it pass in producing the cells of which vege- 
tables are composed. 
In a series of sections of the extremity of a root of the date- 
tree, consequently at the point of that root where the cambium is in 
progress of increasing elaboration, he saw in the mucilagimous sub- 
stance a multitude of irregularly-spheroidal homogeneous masses, 
evidently resulting from a concentration of the mucilage, which in 
each condensed mass already exhibited the earliest rudiments of 
future organization. In the centre of each mass a cavity is soon 
formed, which gradually enlarges, and accumulates around it the 
matter by which it is bounded ; and this matter, thus moulded, 
being expanded into a membrane by the dilatation of the cen- 
tral cavity, finally represents a hollow sphere, which is nothing 
more than a vesicle moulded by the cavity which it circumscribes. 
In this manner, by a kind of eccentric condensation of the mu- 
cilaginous cambium, the walls of the vegetable cells are formed, 
and the amorphous matter passes, under the observer’s eye, from 
the state of diffusion into active life, and thus becomes suscep- 
2H2 
