United States or Burkina Faso ? Vote for the TOP Country of the Week !
He has all the characteristics of structure and development that distinguish the Placentals from the two lower divisions of the mammals, and, in fact, from all other animals. Among these characteristics we must especially notice the more advanced development of the brain. The fore-brain or cerebrum especially is much more developed in them than in the lower animals.
Brain and spinal cord of the frog. Brain of an ox-embryo, two inches in length. Thus, while the brain of the mammals agrees a good deal in general growth with that of the birds and reptiles, there are some striking differences between the two. In the mammals these parts do not grow, and the fore-brain develops so much that it overlies the other vesicles.
The fore-brain or cerebrum, in particular, is so small that it does not cover the cerebellum. Like these, the Monotremes have a strongly developed caracoideum. From these and other less prominent characteristics it follows absolutely that the Monotremes occupy the lowest place among the Mammals, and represent a transitional group between the Tocosauria and the rest of the Mammals.
So that the correspondence in general structure, in the minute structure of the tissues, in chemical composition and in constitution, between man and the higher animals, especially the anthropomorphous apes, is extremely close. Shows a human embryo, from Ecker, and a dog embryo, from Bischoff. Labelled in each are: a. Fore-brain, cerebral hemispheres, etc. b. Mid-brain, corpora quadrigemina. c.
Word Of The Day