Page:Popular Science Monthly Volume 69.djvu/9



MBRYOLOGY is the most complex subject in the domain of science. Living beings are the most complex objects which nature offers us for study, and of this great class the higher animals exceed all others in complexity. The anatomist who studies the structure of the adult has a finished apparatus to investigate; a machine which has been perfected, in which, to be sure, nature may still make repairs, but in the pattern of which she makes no radical changes. The physiologist deals with this machine at work. The embryologist, on the contrary, has for his theme the history of this machine and of its gradual production from a single cell and the progeny thereof. During the period of development the machine at every stage is a different machine from that which it was in the stage before and which it will become in the stage after, and yet in every stage it is actively at work performing its proper physiological functions. We have to deal not with a condition, but with a series of conditions, each of which is at once the consequence of that which went before and the cause of that which is to follow. The final problem of embryology is to determine the origin and cause of the structure of the living body, and incidentally it has to deal with the associated problems of teratology, growth, heredity and sex.

We acknowledge the immensity of the questions for which embryological science must seek answers, but it is far from my intention