Address to the Anthropological Section of the British Association / by Sir William Turner.

  • Turner, Wm. (William), Sir, 1832-1916.
Date:
[1889]
Catalogue details

Licence: Public Domain Mark

Credit: Address to the Anthropological Section of the British Association / by Sir William Turner. Source: Wellcome Collection.

Provider: This material has been provided by The Royal College of Surgeons of England. The original may be consulted at The Royal College of Surgeons of England.

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    As presiding over the proceedings of the Section on this occasion, it is a part of my duty to open its public business with an address. For me, as doubtless for many of those who have preceded me in this honourable ollice, one's mind has been somewhat exercised in the choice of a subject. In a branch of bioloLncal science so vast as Anthropology, in which the room for selection is so ample, the difficulty of making a choice is perhaps still further increased. As a professional anatouiist, whose life's work it has been to study the structure of the human body in its normal aspects, to inquire into the variations which it exhibils in dilferent indi- viduals, and to compare its structure with that of various forms of animal life, it at first occurred to me that an address on the physical characteristics of some of the races of men would be appropriate. But further consideration led me to think that such a subject would be too technical for a general audience, and that it might perhaps be productive of gi-eater interest on the part of my auditors if I selected a topic which, whilst strictly scientific in all its bearings, yet appeals more dis- tinctly to the popular mind, and is now attracting attention. Hence I have chosen the subject of Heredity, by which 1 mean that special property through wiiich the peculiarities of an organism are transmitted to its descendants throughout succes- sive generations, so that the offspring, in their main features, resemble their parents. The subject of Heredity, if I may say so. is in the air at the present time. The journals and magazines, both scientific and literary, are continually discussing it, and valuable treatises on the subject are appearing at frequent intervals. But though so important a topic of existing scientific thought and speculation, it is by no means a new subject, and certain of its aspects were under diseuasion so far back as the time of Aristotle. The prominence whic'i it has assumed of late years is in connection with its bearing on the Darwinian Theory of Natural Selection, and, consequently, biologists generally have had their attention directed to it. But in its relations to Man, his structure, functions, and diseases, it has long occupied a prominent position in the minds of anatomists, physiologists, and physicians. That certain diseases, for example, are hereditary was recognised by Flippocrates, who stated generally that hereditary diseases are difficult to remove, and the influence which the hereditary transmission of disease exercises upon the duration of life is the subject of a chapter in numerous works on practical medicine, and forms an important element in the valuation of lives for life insurance. The first aspect of the question which has to be determined is whether any physical basis can be found for Heredity. Is there any evidence that the two parents contribute each a portion of its substance to the production of the offspring so that a physical continuity is established between successive generations ? The careful study, especially during the last few years, of the development of a number of species of auimals mostly but not exclusively amongst the Invertebrata, by various observers, of whom I may especially name Biitschli, Fol, E. Van BenedcM, and Hertwig, has established the important fact that the young animal arises by the fusion within the egg or germ-cell of an extremely minute particle derived from the male parent with an almost equally minute particle derived from the germ- cell produced by the female parent. These particles are techuically termed in the former case the male pronucleus, in the latter Xhe female pronucleus, and the body formed by their fusion is called the segmentation nucleus. These nuclei are so small that it seems almost a contradiction in terms to speak of their magnitude; rather one might say their miuimitude, for it requires the hi-rher powers of (he best microscopes to see them and follow out the process of conjugation. But notwithstanding their extreme minuteness, the pronuclei and the segmentation nucleus are complex both in chemical and molecular structure. From the seg- mentation nucleus produced by the fusion of the pronuclei with each other, and from corresponding changes which occur in the protoplasm of the egg which surrounds it, other cells arise by a process of division, and these in tiieir turn also multiply by division. These cells arrange themselves in course of time into layers which are termed the germinal or embryonic layers. From those layers arise all the tissues and organs of the body, both in its embryonic and adult sUges of life.