File:The chemistry and physiology of growth (1949) (19982074884).jpg

Title: The chemistry and physiology of growth
Identifier: chemistryphysiol00parp (find matches)
Year: 1949 (1940s)
Authors: Parpart, Arthur Kemble, 1903-; Princeton University; Northrop, John Howard, 1891-
Subjects: Growth; Biochemistry
Publisher: Princeton, Princeton Univ. Press
Contributing Library: MBLWHOI Library
Digitizing Sponsor: MBLWHOI Library

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DIFFERENTIAL GROWTH I75 shaped pattern. Cell movements and divisions will be directed at the area, instead of around it as in the preceding example. Many embry- onic invaginations (e.g. blastopore, neural tube, nasal pits) seem to take their origin from such localized contractile centers in the surface coat of the germ (24),
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Figure 2. Diagrams illustrating the effect of local contraction (top) and local ex- pansion (bottom) on the structure of a reticular matrix. It was very illuminating to find that certain biochemical activities attending growth and differentiation may lead to the same type of ex- pansion and contraction patterns (45). The expansion type, for in- stance, is observed around areas with proteolytic activity. When a local process dissolves part of an erstwhile coherent protein network, the re- maining portion, owing to its elastic tension, retracts from the hole and assumes a pattern like that shown in Figure 2 Be, much like a pierced cobweb. A contraction pattern such as in Figure 2 Ac, on the other hand,

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