This texture exposed to drying, becomes yellowish, remains pliable and can be bent in any direction; so that the dried venous bands, might in this respect, be applied to uses, to which the arterial could not in the same state.
This texture becomes putrid also more easily than the arterial, but less so than the others, particularly the muscular. To ascertain this, I have exposed at the same time, venous trunks and portions of intestines of fine muscular layers, to the contact of a moist air.
It resists maceration less than the arterial texture, but more than the others; water in which it has been macerated by itself is much less fetid than that in which an equal portion of muscular texture has been placed.
The horny hardening of the venous fibres is very evident when they are plunged into boiling water or the concentrated acids. They contract then more than half, at the same time they become more evident; in this way they can be studied better; I have used it often; their contraction thickens the parietes of the vein. When they are hardened in this way, if they remain in boiling water or the acids, they become soft very soon in the second, more slowly in the first. Boiling acts upon them quicker than upon the arterial fibres; they can also be reduced by long ebullition to a pulpy state, to which we can never bring the arteries.
The caustic alkali seems to have a very remarkable action upon the veins. After remaining a short time in a solution of this alkali, they become diaphanous, diminish in size, do not entirely dissolve, it is true and become liquid, as in the acids, but evidently lose their elementary principles, give a remarkable precipitate, and always render the liquor less strong, by the new combinations which it forms.
II. Parts common to the organization of the Vascular System with Black Blood.
Blood Vessels.
The veins have in their texture little arteries and veins, which take very much the same course as in the arteries. They ramify at first in the cellular membrane, send small branches to the neighbouring parts, then penetrating the venous fibres, wind there in a thousand different directions and finally terminate about the common membrane, which when injected has appeared to me to receive more than in the arteries.
Cellular Texture.
The veins, like the arteries, have around them two kinds of cellular texture; one which is exterior and of the same kind as that which is found in the interstices of all the organs; it contains fat and serum, and serves only to connect the veins with the adjacent organs; the other dense and compact, forms for them a proper coat. No author has yet distinguished the cellular system of this particular texture from that which is generally spread over the organs, though it differs from it so essentially in its filamentary texture, in its dryness, its uniform want of fat and serum, its remarkable power of resistance, &c. When we raise it, by tearing it with the fingers from the veins, it appears as if it was formed of an infinite number of little filaments interwoven with each other.