Hormones and structural development / by Charles R. Stockard.

  • Charles Rupert Stockard
Date:
[1927]
Catalogue details

Licence: In copyright

Credit: Hormones and structural development / by Charles R. Stockard. Source: Wellcome Collection.

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    it initially grows away from the gut wall. If at the time this initial budding out should occur, the general state of the embryo is depressed, the early organ bud may be incapable of developing at a normally rapid rate and its expression is subnormal, slow or completely inhibited. There would seem to be, broadly speaking, critical moments of origin for the organs of the embryo, at which periods it is highly essential that the general develop¬ mental conditions and rate be at their optimum. When we slow the rate of development, we affect that part which chances to be developing at its maximum rate at that time, while the more slowly developing parts are not so seriously injured, if affected at all. We may imagine, for example, that at a certain period several organs are developing at the rates 20, 30, 45 and 80. If the rate of development be then experimentally lowered so that no organ can progress above 30, the organ which should be developing at the rate of 80 is reduced to 30 and will probably be considerably modified by the arrest. The organ at 45 is also reduced to 30 or lower, also to its disadvantage, while the organ at 30 may possibly be able to almost maintain its rate and likewise the one at 20. We might actually imagine that the two latter organs are benefited by being brought to par with organs which had formerly to some extent dominated them. The last suggestion is rather doubtful, however, since even the slowly developing parts might suffer from the arrest, and if they maintained only a low rate when the general developmental rate was high it is very probable that they must also be depressed by a general slowing of the rate. There are then critical moments in the origin and de¬ velopment of organs when they suffer acutely from an unfavorable change in developmental conditions, and there are somewhat passive periods when the given organ may be only slightly affected by the same unfavorable
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