Address of the President. 
23 
history when it is nothing else than an aggregation of cells, 
all apparently similar to each other ; and as in some of the 
tissues — for example, in the blood-corpuscles, fat, cartilage, 
epidermis, epithelium, and the grey matter of the nervous 
centres — the cellular character is preserved throughout life, 
so might it be reasonably inferred that the rest are derived 
from cells, by a metamorphic process whose consecutive 
stages might be traced by microscopic observation. This 
was the problem which Schwann set himself to elucidate, and 
which he has been generally considered to have gone far to 
solve. For although an exception was early taken by 
various observers both on the continent and in this country, 
in regard to that simple fibrous tissue which is formed by the 
fibrillation of the effused blastema or organizable plasma of 
the blood, almost every microscopic observer, down to a very 
recent period, who has devoted himself to this department of 
inquiry, has taken Schwann's idea as his guide, and has con- 
sidered it to be his main object to extend and complete it, 
by more fully elucidating the series of steps by which bone, 
tooth, shell, muscle, nerve, &c., are evolved from the cells in 
which they have have been almost unquestioningly believed 
to originate. 
The doctrine of Schwann and his followers, however, has 
lately been the subject of very acute criticism on the part of 
Mr. Huxley ; who has urged many arguments for the conclu- 
sion, that the cell is not the essential integer of the living 
organism which it has been, and still is, held to be by most 
physiologists ; that it is only one out of many forms of organic 
structure, into whicli the organizable blastema may evolve 
itself; and that many animal tissues may form themselves 
directly out of this blastema, without undergoing the inter- 
mediate condition of cells.* 
Although I am not by any means disposed to go as far as 
Mr. Huxley in abandoning the cell-doctrine of Schwann and 
his followers, yet I cannot but admit the correctness of much 
that he has urged. The essential truth, however, seems to 
me to lie between the two extremes ; in other words, the cell- 
doctrine of Schwann can only be accepted when the word 
"cell" is understood in a sense much wider than that to 
which he limited it ; but when it has been thus modified, 
there does not seem to me to be any adequate reason for 
relinquishing it. Fresh light having been thrown upon the 
subject by recent researches into the lowest types both of 
* See his Memoir on the Cell-Doctrine, in the ' Brit, and For. Med,- 
Chir. Kev,,' vol. xii. ; and his article, ' Tegnmentary Organs,' in the 
' Cyclop, of Anat. and Physiol.,' supplementary volume. 
