General Anatomy, Applied to Physiology and Medicine, Vol. 3 (of 3)Bichat, Xavier
Science
General Anatomy, Applied to Physiology and Medicine, Vol. 3 (of 3)
Bichat, Xavier
Human anatomy; Human physiology
The general internal motion which takes place in the first moments of
existence, and which is produced by the suddenly increased activity
of the involuntary muscles, has an important use with respect to the
mucous surfaces, which it relieves of the fluids that load them,
and whose presence becomes painful. Where the mucous surfaces have
not around them fleshy layers of the involuntary muscles, as in the
bronchia, the nasal fossæ, &c. the muscles of animal life more or less
distant, perform this function, as for example, the diaphragm and the
intercostals, free the bronchial surface by coughing, and the pituitary
by sneezing.
As we recede from the period of birth, the organic muscles grow in
general much less in proportion than the others; it is this that
gradually re-establishes the equilibrium between the two systems. I
would remark however, as it respects the predominance of the first,
that it is much less conspicuous in the fœtus than that of the nervous
system. The brain, for example, is in proportion much larger than the
heart.
It is probable that the muscles of which we are treating, exhibit, at
this period, the same varieties of composition as the others, that
gelatine especially predominates in them, that they have less fibrin,
&c. This last substance perhaps exists, in the early periods, more
abundantly in the heart than in the other muscles of this class.
We have observed two very distinct periods in the growth of the
other muscles; one is finished when they have acquired their length;
the other, when their thickness is complete. The first has not, in
the organic system, a term as distinct; when the stature no longer
increases, the gastric and urinary organs, and the heart still lengthen
and grow.
We have considered growth in too general a manner. Each system has
a different term in this great phenomenon. The osseous and muscular
systems of animal life, and those which depend on them, as the fibrous,
the cartilaginous, &c. have especially an influence upon the general
stature of the body; it is these which produce this or that height; but
this height has no influence upon the length of the intestines, or the
capacity of the stomach, the heart, the bladder, &c. The glandular,
serous, mucous systems, &c. are equally independent of stature; thus
in these numerous varieties, it has much more influence upon the
extremities, than upon the abdomen, the thorax, &c. A great height
indicates the predominance of the apparatus of locomotion, but not of
those of digestion, respiration, &c. The termination of the growth in
height, which we consider in a general manner for the whole body, is
only the termination of the growth of the muscles, the bones and their
dependancies, and not of that of the internal viscera, which still
lengthen and become thicker. It is easy to be convinced of this, by
comparing the organic muscles of a young man of eighteen years, with
those of a man of thirty or forty.
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