Remarks on Quekett's Histology, On Kölliker's Human histology, and on the physiological importance of the nucleus of the cell / by Martin Barry, M.D.

  • Barry, M. (Martin), 1802-1855.
Date:
[1854]
Catalogue details

Licence: Public Domain Mark

Credit: Remarks on Quekett's Histology, On Kölliker's Human histology, and on the physiological importance of the nucleus of the cell / by Martin Barry, M.D. 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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    I found to take place in tliat of the highest class mammalia. I have already stated this cleaN age to be no other than a process of cell-for- mation. With every division the cells are doubled in number, and each brood is smaller than the last. At length they become innu- merable and very small, and are densely grouped into a mulberry- like mass which occupies the centre of a cavity containing colourless transparent fluid. Of this mulberry-like group of cells I gave many drawings.^ It expands into the so-called germinal membrane, thus coming to line with cells the zona or vitellary membrane. Tliis expansion reveals the existence of a cell in the centre of the gi'oup far larger than the rest, and in some instances having a diameter many times that of the cells around it. This large cell, passing to the surface, comes to lie immediately under the vitellary membrane. The primitive trace or rudimental embryo is no other than the altex'ed nucleus of this large cell. Of this cell I gave many draw- ings, as well as of its nucleus.^ These show the gradual alterations by which a round nucleus becomes the club-like primitive trace, or rudimental embiyo. They do not essentially differ from the alterations I found to take place in other nuclei, consisting in the formation of zones continusdly pushed out from a centre. In no instance did I obtain more abundant evidence that changes in and enlargement of the nucleus are initiated by the nucleolus, than was furnished by the very nucleus in question. My drawings show that not only when the nucleus is round, but after it has assumed the club-like form and become the primitive trace, there is a con- tinued origin of new substance in the centre (nucleolus), parts ])re- viously situated there, as I said, having been pushed farther out.'^ Each zone is made up of segments, each segment a young nucleus. Thus the alterations here, as in every other nucleus, consist in con- tinual divisions. This nucleus, then, being the embiyo itself, I conceive that in physiological importance there is no nucleus that can be called its rival. In it we have the main result of that wondrous process of transitory cell-life in which really consists cleavage of the ovum. That process in assimilating spermatozoon and germ-spot, produces the nucleus in question—a third substance, which, thus composed of elements derived from both parents, begins forthwith to be de^ yeloped into oflFspring Inheriting properties from both. How this inheritance is brought about, we probably shall never know. But there is one thing perhaps not undeserving of notice, which is this: that,'as the simplest forms of independent life are reproduced and perpetuate their race by fission, so by fission are reproduced the nuclei composing the most complicated organism; the first of the.se 1 Phil. Trans., 1839. Plate VI. lb. 1840. Plates XXVI., XXVII. 2 Phil, Trans., 1839. Plate VI. figs. 113, 114, 115, IIG bb.; Plate VIII., fig. 148. lb. 1.S40. Plate XXVII., figs. 223 to 228, 232 to 234. » Phil. Trans., 1839. Sects. 212, 266, Plate VIII., fig. 148 ; Plate VII., figs, 118, 121 a, 12] b. . s . . f.