Paper - Embryological and morphological studies on the mid-brain and cerebellum of vertebrates
|Embryology - 22 Jan 2020 Expand to Translate|
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Palmgren A. Embryological and morphological studies on the mid-brain and cerebellum of vertebrates. (1921) Acta Zoologica. 64(5): 2-94.
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Embryological and Morphological Studies on the Mid-Brain and Cerebellum of Vertebrates
With 119 figures in the text.
|I. The Mesencephalon
||II. The Cerebellum|
The embryological development of the vertebrate brain from various points of view ,has been examined by a great number of authors. Already v. BAER (1837) stated that the brain oriment (in the chick), after the tri- vesicle stage that had previously been described, divides into five vesicles that he named ”Vorde-r-, Zwischen—, Mittel—, Hinter— and Nachhirn”. HUXLEY (1871) called these five vesicles: ”Prosencephalon (Telencephalon according to the present nomenclature), ’I‘hala.mencephalon, Mesencephalon, Metencephalon and Myelencephalon”. Thanks to GOETTE (I875), MIHALKOWICZ (1877), and other authors our knowledge of the chief characteristics of the morphogeny of the brain was increased. ,
Undoubtedly His and KUPFFER’S works denote great progress. His ”Zur allgeme-inen Morphologie des Gehirns” and KUPFFER’S ”Studien zur vengleichenden Enltwicklungsgeschichte des Kopfes der Kranioten” and ”Die Mor ho enie des Centralnervens stems” treats a number of ortant details in the development of the brain in all vertebrates. In the work last-mentioned KUPFFER has collected and by numerous observations of his own supplemented the results of the monphogenetic. investigations in lower vertebrates. Not only HIS but also GR6NBERG (I901), ZIEHEN (1905), and others have occupied themselves more especially w.ith researches on the development of the mammalian and human brain.
The much debated question of the segmentation of the head excited interest to study more closely the segmentation of .the central nervous system in earlier stages of development. A review of the literature of these questions is given below.
The works treating the embryological development of the nuclei are, on the other hand, relatively few. Just these investigations appear to me to be of the utmost importance.
The preponderant number of conclusions about homology of various nuclei and portions of the vertebrate brain are inferences founded on similar fibre connections of the nuclei. When a nucleus in a lower animal has been proved to have the same or similar connections as a nucleus in a higher animal, the conclusion drawn therefrom was that these nuclei are homologous. Very often .little or no regard has been paid to the morphological position of the nuclei, and still less to their ontogenetic formation. In the very idea of homology there is a claim that the homologous pontions should be of the same genetic origin. In order to decide if two nuclei, or portions of the brain in two separate types of animals are homologous or not, it is, above all, necessary to investigate, if possible, the embryological origin of these nuclei. If later it can be shown that the nuclei in question have the same fibre connections, then a valuable support is naturally given to the conclusion. fibre connections as decisive factors must be a secondary consideration. In those cases when two brain portions plainly prove to be of the same genetic origin, the nuclei are homologous even if the fibre connections are not precisely the same. The latter are subject to variations in the animal series. Connections existing in a lower animal maybe lacking in a higher, while, on the other hand, here new connections may have arisen. The fibre connections of a nucleus may well be comprehended as an expression of its function in one case or the other. But the function of the nuclei has nothing to do with their homology, that being a purely morphological conception.
If, however, it can be pnoved that two nuclei are formed from the same portion of the neruroblastic layer, thus from the same pontion of a (secondary) segment, they are homologous.
Our knowledge of the ontogenetic development, more especially of the mid-brain portions, is as yet very incomiplote. Certain portions, as Tectum opticum, Nucleus oculomsotorius and Nucleus ruber, have certainly been investigated embryologically, but no more particular and comparative investigation of the formation of the other portions has, so far as I am aware, been undertaken. A comparative investigation of the .mi.d—brain in ver-tebrartes appears to me to be the basis on which the morphology of the mid- brain can be fOUz1'l‘dCl(l. In the following pages I have tried to carry out such an investigation.
These studies have been carried on during the years 1919 and 1920, at the Zoortomical Institute of the Stockholms Hogskola. Thanks to the extreme kindness of the prefect of the Institute, Professor Dr NILs HOLMGREN, I have been enabled to investigate a portion of the material for research and the abundant collection of neurological preparations belonging to the Institute. For these advantages and the many hints and the interest that Professor HOLMGREN has constantly shown in my investigations I wish to thank him most sincerely.
Material and Method
The examined speciesand embryological stages are the following:
Selachii: Acanthias vulgaris, stages of LI; 1,4; 1,5; I,8; 2,0; 2,3; 2,5; 2,7; 3,2; 3,9; 5,0; 5,5; 6,5; 8,0; and 15,0 cm. ho-dylength measured before the fixation. fixation in Carnoys ﬂuid. Stain: haemalum according to Mayer or Cresyl violet.
Ganoidei: I) Acipenser mthenus, adult. fixation in alkohol. Stain: iron haematoxyl.in according to Heindenhain- One series of transverse sections.
2) Lepidosteus osseus, of 13,0 cm. bodylength. fixation in alkohol. Stain: Cresyl violet. Two series of transverse sections.
Teleostii: 1) Salmo salvelinus, stages of 0,6; 0,7; 0,8; 0,9; 1,0; 1,1; 1,2 cm. bodylength and,.of I (A), 3 (B), IO (C), 46 (D) and 64 (E) days after hatching. fixation in Bouins ﬂuid. Stain: haemalum according to Mayer.
2) Adult brains of Salmo salz/elimts, Osmerus eperlanus, Labms rupestris and others.
Amphibia: Rana temporaria, stages of 0,4; 0,5; 0,6_; 0,7; 0,8; 1,0; 1,5; 2,0; 3,0; 3,6 cm. bodylength and newly metamorphosed young and adult frogs. fixation in Bouins ﬂuid. Stain: haemalum according to Mayer.
Reptilia: Tropidonotus matrix, a stage with four body spirals. fixation in alkohol. Stain: haemalum.
Aves: Callus domesticus, stages of 50, 60 hours and 4, 4%, 5, 6, 7, 8, 8%, 9, I0, I 5, 19 days of incubati.on. fixation in Bouins ﬂuid. Stain: haemalum acconding to Mayer or Cresyl violet.
M ammalia: Mus musculus var. albino, stages of 0,5; 0,55; 0,6; 0,7; 0,8; 1,0; 1,3; 1,6; 1,9; 2,3; 4,0; 4,5 cm. bodylengtwh and adult specimens. fixation in Bouins ﬂuid. Stain: haemalum according to Mayer or Cresyl violet.
Cite this page: Hill, M.A. (2020, January 22) Embryology Paper - Embryological and morphological studies on the mid-brain and cerebellum of vertebrates. Retrieved from https://embryology.med.unsw.edu.au/embryology/index.php/Paper_-_Embryological_and_morphological_studies_on_the_mid-brain_and_cerebellum_of_vertebrates
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