H1S, ON THE CORNEA. on 
a line or a line in breadth. These vessels are developed by 
the anastomosis and coalescence with one another, and with 
the pre-existing vessels, of certain of the peripheral sacs con- 
taining cells whose origin is explained in the foregoing ex- 
tract: but for the details of these and the other changes 
which the corneal cells have undergone, we must refer to the 
original. Suffice it to say, that from first to last, every new 
histological element proceeds from the metamorphosis of 
those which pre-existed. Nothing but nutritive material is 
derived from without. 
“As the general result of the observations which have been detailed, we 
must place in the front rank the complete confirmation of the law already 
laid down by Virchow, ¢hat in inflammation of the cornea no free, indepen- 
dently distinguishable exudation exists. Neither is there an exudation into 
supposed interstices of the tissue, nor can any turbidity of the intercellular 
substance be observed, which can be regarded as the result of an exudation. 
All the changes which the cornea undergoes take place in the pre-existing 
elements of the tissue, and everyinflammatory opacity, softening, and desqua- 
mation that has hitherto been regarded as serous or fibrinous exudation ; every 
newly formed vessel and substance of a cicatrix, is the immediate product of 
altered corneal cells and their derivatives. It is only as a secondary result 
that the pre-existing intercellular substance undergoes changes, which are, 
as it were, imposed upon it by the changed energies of the cellular elements. 
Hence, in establishing a theory of corneal inflammation, our aim must be to 
study the laws of the changes of the cellular elements, their causes, and con- 
sequences, and to substitute determinate histological principles capable of 
scientific elaboration, in the place of the obscure notion of corneal exuda- 
tion.” —pp. 108-9. 
Reviewing his results with this object, Dr. His arrives at 
some singularly interesting conclusions. He conceives that 
three types may be distinguished among the modifications 
undergone by the corneal cells when subjected to inflamma- 
tory iritation—the first, in the cells about the neighbour- 
hood of the point of irritation; the second, in the superficial 
cells of the margin of the cornea; and the third, in the cells 
of all the deeper corneal layers. In all these cases the intro- 
ductory changes are the same; the cells increase in size; 
their nuclei divide, and their contents become retracted, and 
undergo segmentation; but in their further progress each 
type of cell differs from the other, not so much in the kind, 
as in the quantity and proportion, of the changes which it 
undergoes. In the deep layers the process is slow and im- 
perfect ; in the highly irritated central part, the cells increase 
but little im size, but their nuclei undergo rapid and frequent 
division ; in the periphery, on the contrary, the increase in 
size is great, and the subdivision of the nuclei falls far short of 
that observed in the central part. 
“In other words, the division of the nucleus is an activity of the cell, 
whereby the latter reacts when stimulated, quite independently of vascular 
