Researches on the primary stages of histogenesis and histolysis / by Robert D. Lyons, M.B.T.C.D., M.R.I.A. (Honorary Professor of Anatomy to the Royal Dublin Society, etc.).

  • Lyons, Robert D. (Robert Dyer), 1826-1886
Date:
1853
Catalogue details

Licence: Public Domain Mark

Credit: Researches on the primary stages of histogenesis and histolysis / by Robert D. Lyons, M.B.T.C.D., M.R.I.A. (Honorary Professor of Anatomy to the Royal Dublin Society, etc.). Source: Wellcome Collection.

Provider: This material has been provided by The University of Glasgow Library. The original may be consulted at The University of Glasgow Library.

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    as elaborated by these and other observers, and specially ap- plied to the development of animal structures by Schwann, fully and satisfactorily explains the mode of formation and de- velopment of several tissues and organs. Notwithstandmg, however, the reception of this theory, even in its extreme and exclusive application, as insisted on by Schwann, inmost schools, soon after its promulgation, it has been found defective in many points, and has been and is still questioned by several observers of authority. Having devoted much attention to this subject, I have become convinced by repeated observations that there are several tissues which at no period of their development exhibit any evidence of formation by cells, and consequently that cells cannot be considered as the only plastic germs or formative elements of organic life. The following researches and observations appear to me to support the opinion now stated. As the common hen's egg offers great facilities for the study of the formation of structures, 1 have made some careful ob- servations of the microscopic elements, which it presents both before incubation and at certain periods after the commence- ment of that process. 1. A portion taken from the mass of the yolk, and sub- mitted to a power of 420 D., exhibited the following elements: a. An abundance of minute granules, covering the greater part of the field, of a light-yellowish colour, with a dark border • and semi-opaque centre, moving freely on each other, and pre- senting the Brownian movement. b. Bodies of larger size, strongly refractive, varying in dia- meter, and evidently oil-globules. c. Vesicles of various sizes, romid, oval, and elhptical, some presenting coarsely granular contents, others extremely fine, almost homogeneous, contents, their borders uniformly clear, dark, but fine, and readily seen; these vesicles were, some as large as ordinary cells, others as small as nuclei. In none could I detect anything like a nucleus or nucleolus.