The Elements of Embryology

Abstract

“STEP by step the simple two-layered blastoderm [of the hen's egg] is converted into the complicated organism of the chick” The separate cells of which it is originally composed have, to all appearances, the most uncomplicated relations one to another; nevertheless, in accordance with laws of which we have not the least conception, under the influence of slight external warmth, by a series of fissures, inflections, and developments in special directions, they convert the store of albuminous material that, together with them, is included within the egg-shell, into an organism so elaborate as a fully developed bird, which can run about and feed itself immediately it makes its appearance in the theatre of active life. The physicist, thoroughly acquainted as he may be with all the principles of statics, dynamics, heat, light, and electricity, finds himself quite at a loss to explain or to predict any single one of the numerous changes which have taken or will take place in this blastodermic membrane during any period, however short, that it has been the subject of observation. Neither the chemist nor the physiologist will find himself in any more advantageous position, except that the latter, from previous experience, will be able to state dogmatically the succession of the steps of the developmental process. We group these phenomena, apparently so extra-physical, under the term “vital” and if at any time it should be shown, which is well within the region of possibility; that they depend on the manifestation of a force other than one of those with which we are at present acquainted, the disciples of the “vitalistic” school will have reason to exult over those “physicists” who do not admit the existence of any yet undiscovered mode of motion. As yet, the fact that one's parents in their earliest days went through the same changes as oneself is not considered a sufficient basis for any logical hypothesis on the subject of the progressive development of one's constituent elements.

The Elements of Embryology.

By M. Foster Francis M. Balfour. Part 1. (London: Macmillan and Co., 1874.)