. The American journal of anatomy . men, but subsequently the cavity becomesfilled up with a solid cell mass which is apparently due to a pro-liferation of the former endothelial or lining cells. Such cellaggregations gradually vanish in the mesenchyme perhaps by theregression of their elements to undifferentiated tissue. In otherwords, the cells which at one time functioned as the limiting wallsof a haemal vessel, after the elimination of such a vessel from theblood channel system, lose their specialized characteristics andpossibly return to the mesenchyme by assuming the qualities andfunctio
. The American journal of anatomy . men, but subsequently the cavity becomesfilled up with a solid cell mass which is apparently due to a pro-liferation of the former endothelial or lining cells. Such cellaggregations gradually vanish in the mesenchyme perhaps by theregression of their elements to undifferentiated tissue. In otherwords, the cells which at one time functioned as the limiting wallsof a haemal vessel, after the elimination of such a vessel from theblood channel system, lose their specialized characteristics andpossibly return to the mesenchyme by assuming the qualities andfunctions of the ordinary tissue cell. By comparing the recon-structions illustrated in figures 28 and 35, it is seen that the venousplexuses which are so profusely developed in the 19 mm. embryohave almost entirely disappeared in an embryo of somewhatgreater length. In the stained sections of the latter, however,some of the dense cellular masses are still visible here and there in 432 OTTO F. KAMPMEIER • > . ■» * ;■ •- *. •. Fig. 10 Transverse section through the upper thoracic region in a 20 mm. (series 194, slide 26, section 21), X 150. 4-d, potential lymphatic anlage inthe right thoracic duct line; 4-s, lymph space in the left duct line; 7, oblique vessel,here plexiform; 8, dorsal segmental vein; 10, left precardinal; 13, aorta; 17,oesophagus. (Reconstruction, fig. 29.) the territory formerly traversed by the temporary venous plex-uses. In series 194 (20 mm. embryo) the atrophy of the oblique ves-sel (7) and its replacement by lymphatics has begun anteriorly,where it is supplanted to a greater or lesser degree by perivenousspaces (4-d, fig. 29) which reflect the features of those further for-ward but are smaller and less conspicuous by reason of the greatersimplicity of the vessel replaced. Along the second half of itscourse lymphatic anlagen are met with which are not formed insuch intimate relations but lie ventral to and not closely in contactwith it. F
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectanatomy, bookyear1912
