98 REPORT—1874, 
from the spleen it is one to sixty, Every organ and every tissue changes this fluid; 
and, to my mind, perhaps the most stupendous miracle of organization is the 
steady maintenance of but slightly variable characters in the living and moving 
blood, which is every moment undergoing changes of different kinds as it circulates 
through each tissue and organ in the body. 
Yet with all this change there is an invariable transmission of the parental cha- 
racters by continual descent from particle to particle as each takes the place of a 
former one; and thus each organ continues to discharge the same function from 
year to year. Animals of the same kind retain the old number of organs, the same 
shape of body, and similar modes of life. There is no sign of commencing life, no 
coining of new vital power, no production of living out of dead matter, The 
original life extends its limits ; it operates in a more extended sphere ; but it is the 
same life, it operates in the same way, it never fails to be recognizable in the in- 
dividual by the same characters as it had when it was first Inown. Whatever 
other functions it discharges, it acts continually in obedience to the first great law; 
it increases and multiplies and replenishes the earth. 
Let us now for a = moments compare our former views of the structure of 
animal membranes with the present ones. The skin (covering the outer surface of 
the body), the mucous membranes, the serous linings of the great internal cavities 
and of the blood- and lymph-vessels, and the lining membranes of joints were all 
alike viewed as if formed of a definite membrane covered on one side by cells, and 
on the other supplied by blood- and lymph-yessels and by nerves—the membrane 
covering in the latter parts and effecting an absolute separation of the cells from 
the vessels and nerves, which were universally believed never to penetrate into the 
cellular layer. The cells were regarded as the parts actively engaged in the per- 
formance of the functions, the vessels and nerves aiding thereto supplying materials 
to be acted on by the cells, and the nerves regulating the amount of action at par- 
ticular times for special purposes. The diseased conditions, like the functions, were 
kept perfectly distinct; and we had one set of diseases of the epithelial or cellular 
arts, and another and a different set of diseases of the membranes and of the parts 
elow. 
I think the first occasion on which the public faith in these views was seriously 
shaken was when the late distinguished Professor of Medicine in St, Andrews, Dr. 
John Reid, died of what was called an epithelial cancer of the tongue. Microsco- 
pical examinations showed that the disease existed in the cellular covering of the 
tongue. <A sufficient cause for it was supposed to exist in the irritation caused b 
sharp points of the teeth, to cover which a protecting silver plate was constructed. 
The diseased parts were removed with the greatest skill and care by Sir William. 
Fergusson, and subsequently by the late Dr. sor Duncan, assisted by Mr. Goodsir 
and Mr. Spence, now Professor of Surgery in-the University of Edinburgh. Every 
conceivable care was taken by these attached friends of the poor sufferer to remove 
every trace of the disease; but it progressed steadily and destroyed this valuable 
life. 
At this period no one could understand the extension of an epithelial disease 
through a basement membrane; and therefore the affection of the adjacent lym- 
phatic glands was explained by supposing the diseased action to have been propa- 
gated from cell to cell along the epithelial surface of the lymphatie vessels. 
Not long afterwards the sternly truthful and accurate Sir James Paget declared, 
in terms of terrible significance to the sufferers from this disease, that epithelial 
cancer takes a little longer time than ordinary cancer to do its fatal work. 
And it soon became thoroughly well known that the glands of the skin, the hair- 
bulbs, and the teeth are produced by a local development of the deep cells of the cu- 
ticle, extending far below the line of the basement membrane or cutis, and through 
the position which it was supposed to occupy, as though no membrane were there to 
hinder them. 
Thus the basement membrane which was supposed so arbitrarily to separate the 
cells on one surface of membranes from the vessels and nerves on the other, gives 
way at once before an increased development of the cells, whether in the formation 
of new organs or the extension of disease. And the membranous walls of capillary 
blood-vessels allow the corpuscles of the blood to pass through them much in the 
