. The cyclopædia of anatomy and physiology. Anatomy; Physiology; Zoology. LYMPHATIC AND LACTEAL SYSTEM. 209 great variety of opinion with respect to the na- ture of its tissue. Breschet and many other anatomists describe this tunic as resembling the cellular coat of the bloodvessels, and are under the impression that the lymphatics are altogether deficient in that which is analogous to the middle or fibrous coat of the arteries and veins. Mascagni and Rudophi have not been able to detect muscular fibres in it. Cruveilhier conceives it to be composed of the tissu jaune elastique, or tissu darto
. The cyclopædia of anatomy and physiology. Anatomy; Physiology; Zoology. LYMPHATIC AND LACTEAL SYSTEM. 209 great variety of opinion with respect to the na- ture of its tissue. Breschet and many other anatomists describe this tunic as resembling the cellular coat of the bloodvessels, and are under the impression that the lymphatics are altogether deficient in that which is analogous to the middle or fibrous coat of the arteries and veins. Mascagni and Rudophi have not been able to detect muscular fibres in it. Cruveilhier conceives it to be composed of the tissu jaune elastique, or tissu dartoide. Schreger thinks he has seen circular muscular fibres in the thoracic duct of man and of large animals, and Sheldon states that he has distinctly seen muscular fibres in the thoracic duct of the horse. By placing a portion of the thoracic duct or large lymphatic laid open with the lining membrane uppermost, on a piece of glass, and by scra- ping off the internal membrane, the fibrous tunic will be exposed ; if it be now moistened with a drop of water, and a piece of talc placed over it, it may be readily examined under the microscope. I have several times examined portions of the thoracic duct and of the larger lymphatics taken from the horse, and from the human subject, and have invariably found the tunic exposed on removing the lining mem- brane, to be composed of fibres passing princi- pally in the longitudinal direction ; these fibres are uniform and cylindrical, and resemble in these respects the organic muscular fibre as de- scribed by Schwann ; they lie for the most part parallel with each other, and are occasionally seen to form a large fasciculus, somewhat analo- gous to the longitudinal muscular bands of the large intestine. These fibres measure from l-5000th to l-6000th of an inch in diameter, and present at intervals, a sudden zigzag inflec- tion ; several fibres collected together into a sort of primitive fasciculus are bent together at the same points. These
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