Purchase of this book includes free trial access to www.million-books.com where you can read more than a million books for free. This is an OCR edition with typos. Excerpt from book: of the cavity being filled by fatty tissue (No. 105). This marked change in the relative size of the cranial cavity and brain takes place mostly in post-larval stages, the unequal development of skull and brain being most marked anteriorly. By it the floor of the anterior part of the skull, and its perforations, are carried forward relatively to the brain, and the optic nerves at their origin are, on the contrary, pulled relatively backward; so that, while in the young they issue in front of the canalis transver- sus and internal carotid canals, they lie in the adult either directly above the internal openings of the carotid canals or even behind them. The olfactory branches of the carotids must, therefore, first run backward under the optic nerves and then forward above them to reach their destination. 4. Nervus and Lobua Olfactoriua. The lobus olfactorius, Goronowitsch, or bulbus olfactorius, Sagemehl, is in the adult Amia a well-rounded mass (lol, Figs. 25 and 64, Pis. XXV and XXXVIII), lying close to the middle line of the head, on either side, immediately above the transverse bar of cartilage marking the front end of the eye-muscle canal, immediately in front of the optic chiasma, and immediately behind the pad of tissue behind and under which the nervus opticus enters the orbit. Its diameter is about one and one half times that of the nervus olfactorius, and it contains, as Goronowitsch has stated, a small lateral extension or diverticu- lum of the ventricle of the fore-brain. On its upper surface, in well-preserved specimens, there are three slight furrows, one running medianward and backward from the lateral surface of the lobus, near its anterior end, one laterally and backward from the median surface of the lobus, and the third directly, backward along the median …
