Atlas and epitome of human histology and microscopic anatomy / by Johannes Sobotta ; edited, with extensive additions, by G. Carl Huber.

  • Sobotta Johannes, 1869-1945.
Date:
1903
Catalogue details

Licence: In copyright

Credit: Atlas and epitome of human histology and microscopic anatomy / by Johannes Sobotta ; edited, with extensive additions, by G. Carl Huber. Source: Wellcome Collection.

Provider: This material has been provided by the Royal College of Physicians of Edinburgh. The original may be consulted at the Royal College of Physicians of Edinburgh.

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    so-callfd .skein stage or propha.se ; this is followed by the second stage, that of the e(puitorial plate or monaster; third, the stage of nietakinesis ; fourth, the stage of the daughter stars or diaster, the nieta[)ha,se ; fifth, the pha.se of the daughter skeins, the anaphase ; sixth, that of the daughter luielei, the telo[)hase. The structural changes manifested in the .several phases of mitosis are e.s.sentially as follows:^ The nucleus of the cell engaged in the preparatory stages of cell division presents a peeuliar rc'arrangeim'nt of its chromatin, which begins to be grouped into diatmct JUament.'<. This arrange- ment beeomes more and more detinite, until gradually a certain number of distinct single threads ai’e found. These distinct chromatic threads are known as chroiiio- .'iome.'i. The number of chromo.somes is constant in the mitotically dividing cells of each species of animal. In the higher animals the number twenty-four predominates,- while many lower animals have onlv four and some only two. In certain cells the.se chromo.somes are verv short, in some ca.ses even gramdar in shape. Jt is not absolutelv certain whether this constancy of the number of chromo- .somes prevails in the cells of all human ti.ssnes, although theoretically this ought to be the (;ase. The chnjinosomes usually a[)p(>ar in the form of loops ; that i.s, each chromosome is l)ent at the middle at an angle. The scattered chromosomes now form a c/o.sc .-^keia (spirem), in which the loops are, a.s a I'ule, so arrangx'd that the closed |)ortion of tin; loop points toward one ])oint of the pei-iphei-y of the nneleus, the so-called pole fic/d, while the free emis of tlie loops point in the o|)posit(‘ direction, the antipole field. .At this stage the eentro- .sonie, which remained at rest dm-ing the condition of lal)il(> erpiilibrium of the cell, beeomes active, assumes a position in the |)ol(; tield of the s|)irem, and appears to send deli- cate rays in all directions. In tlu' stag(‘ of tlu' loom’ nh-eiu ‘ Tlie in'ocess is nr)t (iiiin- ttii; siiinc in all iiiito.se.s. The variations which occur arc, however, unessential.