. Chemical embryology. Embryology. SECT. 2] AND WEIGHT 443 stomach until the end of the embryonic period. It is certainly in- teresting that organs so different in origin and nature as the eye and the mesonephros should be similarly affected by spurts of growth at various stages, and Schmalhausen concluded that this was an argument against the hypothesis of specific organ-stimulating sub- stances, the presence of which would from time to time cause more. 0 1 Z 3 V 5 6 7 a 3 10'^ 1Z ^3 1'^ -75 16 17 13 13 20 Zi Days Fig. 57. C = brain; £; = hind limb; A"=whole body; Z-t = liver; Li = lens;
. Chemical embryology. Embryology. SECT. 2] AND WEIGHT 443 stomach until the end of the embryonic period. It is certainly in- teresting that organs so different in origin and nature as the eye and the mesonephros should be similarly affected by spurts of growth at various stages, and Schmalhausen concluded that this was an argument against the hypothesis of specific organ-stimulating sub- stances, the presence of which would from time to time cause more. 0 1 Z 3 V 5 6 7 a 3 10'^ 1Z ^3 1'^ -75 16 17 13 13 20 Zi Days Fig. 57. C = brain; £; = hind limb; A"=whole body; Z-t = liver; Li = lens; Af=mesone- phros; Oc = eye; P = lung; Af/n = metanephros; 5^ = stomach; G=gonads. rapid growth in one place of the embryo than in another. It looks much more as if growth-promoting substances were passed round in the embryonic circulation at certain definite intervals, and so exercised an effect on a large number of different organs. In this connection, the recent work on the growth-promoting substances of egg-yolk should be borne in mind, and the experimentally deter- mined cycles of varying permeability to fat-soluble and water- soluble substances in the walls of the vitelline blood-vessels. One relation which seems clear from Schmalhausen's work is that growth. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Needham, Joseph, 1900-. New York: The MacMillan Co.
Size: 1684px × 1483px
Photo credit: © Library Book Collection / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1900, bookpublishernewyorkthem, booksubjectembryology
