It is in the second month of life in the womb that the fish form of brain is distinctly apparent, as shown by Tiedemann. The fish form is that in which we have only a rudiment of the cerebrum, which is so large in man. Behind the little cerebrum, which is smaller than the bulb of the olfactory nerve, we have the middle brain or optic lobes, which give origin to the optic nerves, and behind them the cerebellum. Let it be understood that the cerebrum is the psychic brain, the cerebellum the physiological brain, and the optic lobes the intermediate or psycho-physiological brain, not sufficient to give the animal its character and propensities, but sufficient to guide it in swimming about. [Illustration] What the cerebrum is when fully developed in man has already been shown; what it is in the fishy stage of development, when it is the smaller portion of the brain, may be understood by a dissection given in Serres "Anatomie Comparée du Cerveau," representing the brain of the codfish dissected or opened from above. In this figure H is the spinal cord, E the cerebellum, C the optic lobes divided, and B the cerebrum divided, showing the radiating fibres of the corpus striatum, m, from which the cerebrum begins its development. When animal life reaches a high development, the functions which are diffused become concentrated into special organs. Intelligence or psychic life is concentrated in the cerebrum, and entirely removed from the spinal cord. The physiological energy apart from the psychic, is concentrated in the cerebellum, and thus the intermediate psycho-physiological organ, the optic lobes or quadrigemina, being no longer important, dwindles to become the smallest part of the brain. [Illustration: EXPLANATION.--In the codfish, roach, and flounder, II is the cerebellum, n the optic lobes, in front of which is the cerebrum, from which the olfactory nerve extends forward. Behind the cerebellum is the superior end of the spinal cord. The letter c is placed on the restiform bodies or posterior part of the medulla oblongata of the cod. The engravings show the upper surfaces of the brains, as we look down upon them.] If the reader will look at the sketch of the brains of the codfish, flounder, and roach, as figured by Spurzheim, he will see in each a very small cerebrum, a larger cerebellum, and still larger middle brain or optic lobes. This is the model on which the human brain is first developed, when in the second month it becomes possible to study it with the microscope. It presents to view in the third month three vesicles of soft neurine, the one which is to form the cerebellum being larger than that which is to become the cerebrum.