LAWS OF GROWTH OF THE CELL APPLIED TO 
HUMAN ANATOMY. 
BY ROBERT REYBURN, A. M„ M. D. 
Reprinted from the Maryland Medical Journal, October 7th, 1893. LAWS OF GROWTH OF THE CELL APPLIED TO 
HUMAN ANATOMY. 
BY ROBERT REYBURJN, A, M., M. D. 
Reprinted From the Maryland Medical Journal, October 7th, 1893. LAWS OF GROWTH OF THE CELL APPLIED TO HUMAN 
ANATOMY.* 
BY ROBERT REYBURN, A. M., M. D., 
Professor of Physiology and Clinical 8urgery, Medi- 
cal Department Howard University, Wash- 
ington, D. C. 
Reprinted from the Maryland Medical Journal, October 7th, 1893. 
The human ovum from which all the 
tissues and organs of the adult human 
body are built up is, in the earliest 
stages of the embryonic life, nothing 
more than a simple cell or mass of pro- 
toplasm. 
These masses of protoplasm or cells 
(which form the ova) are practically 
identical in all animals, and consist of a 
fecundated living germ, which has sur- 
rounding it a limited supply of food 
yelk or nourishment. This serves to 
nourish the embryo, until other struc- 
tures are developed, which carry on the 
process of nutrition during the entire 
period of freral existence. 
As the human ovum or egg is di- 
rectly transformed during the process of 
development into the adult human body, 
it is sc 1 f obvious that the laws govern- 
ing the growth of the human ovum 
must be identical with, and furnish the 
key to, the laws governing the growth 
of the organs and structures contained 
in the human body in its adult or com- 
pleted fofm. 
What, then, are these laws? Or rather 
the causes and conditions which modify 
the growth of cells ? 
The first of these conditions here to 
be specified is, that cells grow in size by 
•Read before the Section of Anatomy, Pan Ameri- 
can Medical Congress, September 6,1893. layers of nutriment applied on the outer 
surfaces of the cells. This is always ac- 
companied by a nearly equivalent amount 
of waste material absorbed from their 
inner surfaces. So long as the amount 
of nutritive material absorbed and de- 
posited upon the outer surfaces of the 
cells is greater than the waste from their 
inner surfaces, the cells continue to 
grow and increase in size until the time 
of maturity is reached. 
Just at this point the forces of waste 
and destructive assimilation are bal- 
anced by the powers of the organism to 
absorb and assimilate nutriment. 
After the period of maturity has been 
reached the retrograde process begins. 
The individual cells and in consequence 
the body as a whole, gradually cease to 
absorb and assimilate as much of nutri- 
tive material as is required to supply the 
waste, hence the inevitable result is 
death, the great and pitiless law that 
rules the organic world. 
How then does the human body as a 
whole grow from infancy to maturity? 
Precisely as the individual cells of the 
body do. 
Take, for instance,the development of 
the great arterial trunk of the body, the 
aorta. In the new-born child the aorta 
is a small tube, the lumen of which will 
measure perhaps three-eighths of an inch 
across; when this same child sh ill have 
reached adult manhood his aorta will 
have become a great tube an inch or 
more in diameter. 
This increase in size,it is very evident, 
must have been produced in the way 
above described. As years pass on, 
numberless layers of microscopic tenuity 
have been piled upon the outer surface 
of the aorta, thus increasing the thick- 
ness of its walls. Along, and indeed 
simultaneously with this process, goes 
on the absorption and waste from the 
inner surface of the blood-vessel, in this 
way increasing its internal dimensions. 
This same law is applicable to the 
growth and development of the intesti- 
nal canal with the stomach and acces- 
sory organs of digestion to the develop- 
ment of the Haversian canals and me- 
dullary cavities of bone to the growth of 
the shafrs of the long bones of the ex- 
tremities, and the growth of the limbs. 
Not only is this law of growth true of 
every organ and structure found in the 
body, but it is just as truly applicable 
to the growth of the human body as a 
whole. 
The second of these causes which 
modify the shape of living is their ten- 
dency to grow in the direction in which 
they can find the most abundant sup- 
ply of nutriment. Living cells, when 
found free or floating in the liquids 
of the body, are always found to be cir- 
cular in shape. As found in other parts 
of the body they vary greatly in form and 
size.- Take, for instance the lacunae or 
bone cells as found in human bones; 
these were originally circular or ovoidal 
cells; as the process of transformation 
of cartilage into bone goes on, the cells 
become incased by layers of earthy mat- 
ter surrounding them. This would pre- 
vent the possibility of their absorbing 
sufficient pabulum to provide for their 
nourishment; in order to overcome this 
difficulty the cell in its process of growth 
absorbs certain portions of the earthy 
walls enclosing them, and thus the myr- 
iads of canaliculi orfine tubes which con- 
nect the bone cells and the Haversian 
canals are formed. The canaliculi are 
of course too fine to admit the passage 
of the red or white corpuscles of the 3 
blood, and their nourishment is carried 
on by the liquid plasma. 
Many illustrations of this second law 
are to be met with in the body; it is only 
necessary here to mention the rapid re- 
pair of fractures of the long bones of the 
body, when the fracture occurs just be- 
low the point where the nutrient artery 
enters the bone, as compared with the 
slowness of repair when it occurs just 
above, thus partially cutting off the cir- 
culation of the blood in the part. 
The more perfect ossification of the 
bones of the cranium, as compared with 
the other bones of the body of the new- 
born child, is probably due to the position 
of the foetus, which usually lies sus- 
pended with the head downwards in the 
uterine cavity. 
In fact, it is generally admitted that 
the growth and development of every 
tissue and organ in the body is directly 
proportioned to the amount of the blood 
supply. 
The third cause modifying the form of 
the cells is that each cell, under favor- 
able conditions, tends to reproduce the 
same type of parent cell from which it 
sprang. Bone tends to reproduce bone, 
muscle reproduces muscle, and so in like 
manner do all the tissues and organs of 
the body. In pathological growths we 
do find alien and foreign tissues in 
the diseased parts of the body. Bone, 
for instance, is often developed in epi- 
dermoid cysts, and in parts of the body 
which in health are composed of carti- 
lage and muscle. 
One important fact, however, is to be 
noted in studying the constituents of 
pathological growths, and that is that all 
growths are histologically true to the 
kind of tissues which are formed by the 
layer of the embryo from which they 
originally came. As is well known, the 
human embryo primarily divides into 
two layers, the ectoderm or epiblast 
and theendoderm or hypoblast. A third 
layer is afterwards developed between 
these, which is called the mezoderm or 
mezoblast. Tissues therefore which or- 
iginally sprang from the ectoderm or 
endoderm layer of the embryo do not 
either in normal or pathological growths 
tend to reproduce the tissues which were 
originally formed from the mezodery or 
middle layer of the embryo. 
The fourth cause modifying the shape 
of organic forms is the pressure ofother 
cells upon them during their earlier per- 
iod of development. The flattened shape 
of the cells found in the epideimis, in 
the hair and many other parts of the 
body, is evidently due to this cause, and 
the same result is seen from pressure in 
the multiform shapes of the cells of the 
tissue invaded by cancerous tumors. 
So numerous are the instances to be 
found in the body of these changes of 
shape produced by pressure, that it is 
unnecessary further to dwell upon 
them. 
After maturity the retrogressive 
change or metamorphosis immediately 
begins in the tissues of the body, the 
powers of assimilation of nutriment be- 
come gradually insufficient to keep up 
with the waste of all the structures of the 
organism, and hence the body as a whole 
tends to emaciate. Not only is this the 
case, but the power of the individual cells 
to separate the waste material which is 
formed as the result of their nutrition 
becomes impaired. These waste mate- 
rials as a consequence accumulate, and 
cause thickening of the cell walls of all 4 
parts of the body. One of the most 
striking of the results of this process is 
to be seen in the hardening and calcifi- 
cation of the arteries which is so com- 
monly found in persons of advanced age. 
The tissues themselves tend to degener- 
ate in old persons. Muscle becomes de- 
graded inco fat, and the same process in- 
vades all the connective and other tis- 
sues of the body; a familiar example of 
this is seen in the arcus senilis or fatty 
degeneration of the cornea, which is one 
of the surest signs of the aging of the 
tissues. 
It may perhaps seem necessary to apol- 
ogize for presenting to the readers of the 
Journal such an elementary sketch of 
the growth and development of the hu- 
man body, yet ii is a necessary prelimi- 
nary to my chief object, which is to call 
attention to what 1 believe to be our 
unscientific method of teaching human 
anatomy. 
The ordinary way of teaching human 
anatomy in our medical schools and col- 
leges is to begin by teaching studying the 
bony framework of the adult human 
body. This has always seemed to me to 
be an entirely erroneous method, for it 
adds unnecessary complexity to the study 
and prevents the student from grasping 
the real simplicity of the idea of man’s 
structure, when it is studied from the 
point of view of its being simply a devel- 
opment of the human ovum. 
If we take up the study of chemistry, 
for instance, we never begin by studying 
the more complex compounds first; on 
the contrary, we first master the ele- 
ments out of which the complex bodies 
are formed, and thus proceed from sim- 
plicity to complexity. 
This same statement is true if we take 
up the studies of botany, mineralogy, 
geology, or in fact any of the branches of 
the natural sciences. 
Why,then, do we adopt a different study 
of human anatomy from the one we 
use in the study of all the other branches 
of natural science ? 
My idea, then, of the true way to teach 
human anatomy would be to begin by 
demonstrating the human ovum or 
cell, then the fluids, such as the blood 
and lymph in which the cells are found 
free and floating. After this, study the 
changes produced in the ovum by im- 
pregnation,the segmentation of the ovum 
with the development of the blasto-der- 
mic membrane, and its further division 
into its external and internal layers. 
Study, then, the tissues and organs 
formed from these layers in their order of 
development, then take up the study of 
the development of the third layer of the 
embryo,withthe organs andtissues formed 
from it. The study of human anatomy 
carried on by this method gives to it a 
simplicity and beauty that renders it 
worthy of being numbered among the ex- 
act sciences. 
It may be here remarked chat this 
method is not a new or untried one, for 
several years Professor Piersol, of the 
University of Pennsylvania, has taught 
anatomy by a method similar to the one 
above mentioned, and the writer a num- 
ber of years ago, when teaching anatomy 
in the Medical Department, Georgetown 
University, adopted with success the same 
plan.