Published in Zoology
Friday, 14 April 2017 12:54
1. Brain of lizard is relatively small and simple in proportion to the body.   1. Avian brain is much more developed.   1. Mammalian brain is very large and is most advanced in the animal kingdom.
2. Brain is protected by two meninges. They are outer thick duramater and inner thin piamater.   2. Same as in calotes.   2. Brain is protected three meninges. They are outer thick dura mater, inner thin pia mater and archanoid membrane in between the two meninges.
3. Olfactory lobes are large diferentiated into an olfactory tract or peduncle and olfactory bulb.   3. The o¥actory lobes are very small and greatly covered by the cerebral hemispheres.   3. Olfactory lobes are more distinctly visible on the ventral side of the cerebral hemispheres.
4. There is no tuber culum of olfactorium. Olfactory lobes are enclosed by olfactory ventricle.   4. There are no tube-rculum of olfactorium and olfactory ventricle   4. Each lobe has olfactory peduncle & olfactory bulb. The peduncle ends behind in a slightly renewed elevation the tuberculum of olfactorium.
5. Cerebral hemispheres are oval with narrow antero posterior ends. These are medially separated by a mid-dorsal fissure.   5. Cerebral hemispheres are very large and form about half of the brain.   5. Cerebral hemispheres are triangular in shape and very large and form about half of the brain.
6. Cerebral hemispheres do not cover olfactory and optic lobes but partly overlap the diencephalon.   6. Cerebral hemispheres largely cover olfactory bbes and diencephalon. These do not overlap optic lobes.   6. Cerebral hemispheres largely cover olfactory lobes diencephalon & optic lobes.
7. There is no corpus callosum.   7. There is no corpus callosum.   7. Cerebral hemispheres are and connected with other by a horizontal transverse band-corpus callosum.
8. Fornix is absent.   8. Fornix is absent.   8. Posterior end of corpus callosum bends down and extends forward as fornix.
9. The surface of cerebral hemispheres is smooth and are not differentiated, into lobes.   9. The surface of cerebral hemispheres is smooth and are not differentiated into lobes.   9. Each cerebral hemisphere is differentiated into four lobes - Frontal, parietal, Temporal & Hippo campal.
10. Cerebral cortex is not well developed.   10. Same as in calotes.   10. Cerebral cortex is well developed.
11. Corpora striata are quite conspicuous.   11. Corpora striata are very conspicuous.   11. Corpora striata are less conspicuous
12. Lateral ventricles are unbranched.   12. Same as in calotes.   12. Lateral ventricles are branched.
13. Diencephalon is a small rounded area pressed between the cerebrum and midbrain.   13. Diencephalon is visible on the ventral side and dorsally cov-ered by cerebral hemispheres.   13. Diencephalon is comparatively small and -completely covered with backward extension of cerebral hemispheres.
14. Diencephelon roof is thin and forms anterior choroid plexus.   14. Same as in calotes.   14. The roof of dienceph-alon is thin and highly vascular and forms the anterior choroid plexus.
15. Epiphysial apparatus possess an anterior parietal body and posterior penial body.   15. Epiphysial apparatus possess pineal body as.   15. Same as in columba.
16. Optic thalami are present but middle commissure is lacking.   16. Opticthalamiare well developed but there is no middle commissure.   16. Opticthalami are connected together by a thick band of grey matter called as middle commissure.
17. Pineal eye is present.   17. Absent.   17. Absent.
18. Corpus albicans is absent.   18. Absent.   18. Asmall, rounded body, the corpus albicans or corpus mamillare present behind pituitary body.
19. Two optic lobes are oval and are present dorsally to form corpora bigemina   19. Two optic are large and present laterally to form corpora bigemina.   19. Optic lobes are small and four in number and form as corpora quadri gemina which are covered by cerebellum.
20. The crura cerebri at the floor of midbrain are poorly developed.   20. Crura cerebri are well developed.   20. Crura cerebri are highly developed.
21. Optic lobes are hollow with optocoels.   21. Optocoels are much reduced.   21. Optic lobes are solid and without optocoels.
22. Cerebellum is poorly developed and it is in the form of a flattened ridge at the anterior end of medulla oblongata.   22. Cerebellum is comparatively more developed and divided into two lateral and a median lobe.   22. Cerebellum is very well developed and divided into two lateral lobes and a median lobe.
23. Cerebellum surface is smooth.   23. Cerebellum surface is folded all over.   23. Same as in bird.
24. Cerebellum is not differentiated into lobes.   24. Cerebellum is differentiated into three lobes - a median large, oval central lobe or vermis and pair of very small lateral floccular lobes.   24. Cerebellum is differentiated into five lobes - a median large central lobe or vermis, a pair of smaller lateral lobes and a pair of still smaller floccular lobes.
25. Pons varolii are absent.   25. Same as in calotes.   25. Pons varolii are present and connect the lateral parts of the cerebellum.
26. There is no arbor vitae.   26. Same as in calotes.   26, White matter forms tree-like arbor vitae in grey matter can be seen in the section of cerebellum.
27. Medulla oblongata is not overlapped by the cerebellum.   27. Medulla oblongata is overhung by cerebellum.   27. Same as in cloumba.
28. It has a distinct ventral flexure.   28. Same as in calotes.   28. Ventral flexure is absent.
29. Ventral fissure and ventral pyramids are absent.   29. Same as in calotes.   29. There is a median ventral fissure bordered by two narrow bands - the ventral pyramids.
30. Corpora trapezo-idea are not formed.   30. Corporatrapezoidea are lacking.   30. A pair of oblong patches - corpora trape-zoidea are present just behind pons varolii.
31. The roof of medulla is thin and vascular which forms the posterior choroid plexus   31. The posterior choroid plexus is completely covered with the cerebellum.   31. The roof of medulla is exceptionally thin and forms the posterior choroid plexus.
32. Velum medullae anterius is not formed.   32. Velum medullae i; absent.   32. A thin transparent membrane - Velum medullae anterius forms the roof over the anterior part of the fourth ventricle. This connects the optic lobes with the cerebellum.
33. Velum medullae posterius is absent.   33. Same as in calotes   33. A thin transparent membrane - Velum medullae posterius forms the roof over hind part of the fourth ventricle.

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