TRANSACTIONS OF THE SECTIONS. 97 
were either composed of cells or had been formed of cells—that nucleated cells 
elaborated all the secretions and formed the excretions—that their energy lay at 
the very root of the formation, the reproduction, and the function of every tissue 
and organ, was a revelation of such astounding simplicity as might well upset men’s 
minds and prevent their seeing beyond. 
~ No one who did not live through that time will, I believe, ever realize the 
eagerness and anxiety with which every new statement of the action of cells was 
received and added to the previous knowledge of their amazing power—or, on the 
the other hand, be able to judge of the feeling half akin to disappointment which 
was experienced as each succeeding attack was made on this charming theory, 
showing it to be really human, very human indeed. 
Cells were then understood to constitute the mass of all organs (the liver, spleen, 
kidney, and brain), and to be the main agents in the discharge of their functions— 
to exist and grow upon the definite membranous walls of the glandular vesicles and 
ducts—to be fed by blood brought to the attached surface of membranes which 
seemed almost everywhere to form an absolute separation of the cellular part (the 
potential ed from the non-essential blood- and lymph-vessels, the nerves, and 
framework of the organ. It seemed almost a pity that these little microscopic 
deities should be hampered by the necessities of their own existence, that they 
should need such base things as blood-vessels, nerves, and packing materials. Now 
how strangely are matters changed! What if it should turn out that these appa- 
rently independent little beings are not independent at all—that they are only the 
dilated endings of nerves. To this subject I shall refer again by-and-by. 
This great cell-theory has now given place to what I think is certain knowledge, 
that living matter may move, perform all the functions of assimilation and nutri- 
tion, and reproduce its like without having any of the essential characters of a cell. 
A living mass of protoplasm may change its shape, alter its position, feed and nourish 
itself, and form other matter having the same properties as it has and yet be per- 
fectly devoid of any structure recognizable by the highest powers of the microscope. 
Mr. Lister showed that the contraction of pigment-cells in the skin changes the 
position of the pigment-granules, driving them alternately into the processes and 
the body of the cell. Kiihne, Golubew, and Stricker observed changes of form in 
‘amcebze (whité blood-corpuscles and embryonal capillaries, respectively) after the 
‘application of electrical stimuli; and Briicke observed contraction in the pigment- 
cells of the skin of the chameleon after excitation of the sensory nerves; whilst 
Kiihne noticed contraction in corneal cells after excitation of the corneal nerves, 
Thus obvious movements in fixed cells or masses of protoplasm are proved to 
‘result from the operation of various stimuli, including nervous stimuli. 
But all cells are not fixed. The blood-cells, fixed, as cells of organs, at an early 
period, become free in the blood-fluid and are moved along by the forces which cir- 
culate it until a second time they enter into the composition of the solid tissues by 
penetrating the walls of the blood-vessels and moving along the substance of the 
tissues for purposes which are not yet wholly explicable. 
What naturalist will not at once suggest how frequently this process of alternate 
~fixation and movement of animal forms occurs low down in the scale? and yet how 
“startling is it in man! how impossible to reconcile with our former ideas of 
the existence of membranous coverings, of cells, surfaces, and of gland-ducts! 
‘But, with or without explanation, the facts must be recognized; the floating 
‘blood-cells are really the very cells which once formed the substance of the lym- 
phatic glands, the spleen, and other organs; and they do, in fact, move through the 
“walls of the blood-passages, and wander about freely in what we call solid tissues. 
Our knowledge of this circulating fluid has marvellously increased. The dura- 
tion of the life of any of its particles is but short; they die and their places are 
occupied by others, as was the case with our forefathers, and will be the case with 
ourselves. It is now a matter of observation, which commenced with Hirt of 
‘Zittau, that after every meal an amazing number of white corpuscles are added to the 
blood: breakfast doubles their proportion to the coloured corpuscles in half an hour ; 
‘supper increases their proportion three times; and dinner makes it four times as great. 
They come from such solid glands as the spleen. In the blood going to the spleen, 
a proportion is one to two thousand two hundred and sixty; in be returning 
