. Carnegie Institution of Washington publication. 16 YOUNG TWIN HUMAN EMBRYOS WITH 17-19 PAIRED SOMITES. ends of the cell bodies anastomose freely immediately beneath the ectoderm, but no external limiting membrane is to be distinguished, such as Bardeen (1900) has described in the pig. Williams (1910) in the chick finds the dermatomes exactly similar to the above and is also unable to demonstrate any external limiting membrane. Regarding Bardeen's contention that the dermatome does not form the cutis layer of the skin and really gives rise to muscle tissue only, as he found in the pig, little
. Carnegie Institution of Washington publication. 16 YOUNG TWIN HUMAN EMBRYOS WITH 17-19 PAIRED SOMITES. ends of the cell bodies anastomose freely immediately beneath the ectoderm, but no external limiting membrane is to be distinguished, such as Bardeen (1900) has described in the pig. Williams (1910) in the chick finds the dermatomes exactly similar to the above and is also unable to demonstrate any external limiting membrane. Regarding Bardeen's contention that the dermatome does not form the cutis layer of the skin and really gives rise to muscle tissue only, as he found in the pig, little light can be obtained here. It is significant, how- ever, and partly confirmatory of Bardeen's results, that in the most advanced segments the dermatomes are beginning to recede from contact with the ectoderm and loose mesen- chyme in finding its way between the two at the edges of the dermatome. It is to be expected that this loose mesenchymatous tissue would develop in situ into the cutis layer later on, and, if so, the so-called dermatome would be really all 3. Graphic reconstruction to show the position and relations of the mesodermic somites and the nephrogenic system in Embryo VI. 4. Graphic reconstruction to show the position and relations of the mesodermic somites and nephrogenic system in Embryo V. The numbers refer to the mesodermic somites. For abbreviations sec page Hi. The undifferentiated mesoderm back of the somites is very solid and condensed, and lies in contact with the medullary canal and the ectoderm, no loose tissue whatever inter- vening. The intermediate cell mass at first is cut off from it, forming the nephrogenic cord, but very soon is seen to be fused with the somitic plate on one hand and the splanchnic and somatic mesoderm on the other. This common mass of mesoderm passes into the tail to fuse with the primitive streak. For some distance caudad of the last somite, a peculiar narrow process passes off ven- trally from the undifferentiated
Size: 1934px × 1291px
Photo credit: © Book Worm / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookauthorcarnegie, bookcentury1900, bookdecade1910, bookyear1915
