Magnified view of two ampullulæ turgid with chyle, terminating the lacteal vessels.
826. When a portion of the intestine in this condition of the lacteal vessels is examined under the microscope, there is said to be visible on the villus an oval vesicle, termed an ampullula (fig. [CXCIV].). This vesicle is described as having an aperture at its apex, which it is conceived constitutes the open mouth of the lacteal, and through which the chyle is supposed to be taken up.
View of villi, with the lacteals arising from their surface by open mouths and forming radiated branches. The surface of one of these villi is represented as entirely white, from the lacteals being so turgid with chyle as completely to obscure their orifices and their radiating branches.
827. Mr. Cruikshank, who particularly devoted himself to the study of this part of the absorbent system, states that he had an opportunity of examining these vessels in a person who died suddenly some hours after having taken a hearty meal, and who had been previously in sound health. “In some hundred villi,” he says, “I saw the trunk of the lacteal beginning by radiated branches (fig. [CXCV].). The orifices of these radii were very distinct on the surface of the villus as well as the radii themselves (fig. [CXCV].). There was but one trunk in each villus. The orifices on the villi of the jejunum, as Dr. Hunter said (when I asked him as he viewed them in the microscope how many he thought there might be) were about fifteen or twenty in each villus, and in some I saw them still more numerous” (fig. [CXCV].).
828. The course of the lacteals, from their origin in the villi to their termination in the thoracic duct, has been traced ([687]). It is conjectured that the lymphatics take their origin from every point of the body, but it is admitted that they have not been actually seen even in every organ; still they have been found in so many that it is inferred that they really exist in all, and that in those in which they have not been hitherto detected they have eluded observation on account of their extreme delicacy and transparency and our imperfect means of examining them.
829. Though, like veins, lymphatics anastomose freely with each other, yet they do not proceed from smaller to larger branches and from larger branches to trunks, but continue of nearly the same magnitude from their origin to their termination. They are disposed in two sets, one of which always keeps near the external surface of the body, and the other is deeply seated, accompanying more especially the great trunks of the blood-vessels.