ABSTRACT
This is specimen number 1500 in the Carnegie Collection, designated here as C1500. A normal fetus with a crown-rump length (CR) of 56 mm was collected in 1916. The fetus is estimated to be early in gestational week (GW) 11. The entire fetus was fixed in formalin and was cut in the horizontal plane. The records are not clear regarding section thickness, but the brain is present in 2,400 sections, more than three times the number of 35 µm sections in the GW17 horizontally sectioned brain in the Yakovlev Collection (Bayer and Altman, 2005, Volume 3, Part IX). We estimate that the sections are between 8-10 µm thick. All sections were stained with Bodian’s method to show developing fiber tracts. Since there is no photograph of C1500’s brain before it was embedded and cut, a specimen from Hochstetter (1919) that is comparable in age is used to show the approximate section plane and external features in early GW11 (Figure 2). Levels 1-10, large sections containg the cerebral hemispheres, are shown at low magnification in Plates 36-45. Levels 11-21, small sections containing only the brainstem, are shown at a higher magnification in Plates 46-56. To maximize image size within page space, C1500’s sections are rotated 90˚ (landscape orientation). The anterior part of each section is on the left (page bottom), and the posterior part of each section is on the right (page top).
