half of them were situated near the entrance of the nerve into the cranial cavity (at point a in fig. 25), while the remainder were found along the posterior branch of the nerve near the paraphysis and the pallial wall of the forebrain (at point b in fig. 25). The latter ganglion is situated in close proximity to the base of the

FIG. 25. Diagram showing dorsal view of the anterior end of adult Amia brain. Made from gross dissections with the aid of Weigert preparations of a young Amia 100 mm. long, to show the relation of the profundus nerve to the ramus which innervates the meninges of the forebrain. Also, it shows the relation of the preoptic sympathetic system to the pineal nerve and to the nervus terminalis. × 4.

dorsal sac (fig. 30) and near the origin of the diencephalic sacs of Kingsbury ('97), from the third ventricle. In total mounts of the intra-cranial part of the nerve, sheath cells can be seen surrounding the large nerve cells (fig. 26). The cells show tigroid bodies and are of the same size and character as those of the pro

fundus nerve outside the cranial cavity. However, some of the cells are only half as large as others and the smallest are about the size of the cells of the nervus terminalis.

The fibers that enter the cranial cavity arise from the ramus ophthalmicus superficialis trigemini where the latter is joined by a portion of the profundus nerve as it extends forward from its main ganglion (Allis, '97, plate xxx, fig. 39, opt). From Weigert sections it seems pretty certain that most, if not all, of the fibers that enter the cranial cavity arise from the profundus nerve. As the profundus nerve furnishes a connection between the posterior part of the sympathetic system and the ciliary ganglion, it may well establish a connection from the sympathetic system

FIG. 26. A portion of the ganglion cells from point b in fig. 25. Camera drawing from the most crowded portion of the ganglion, the meninges being mounted without sectioning. Shows sheath cells around the nerve cells and Nissl bodies within. X 200.

to the cells inside the cranial cavity, and to the nervus terminalis. It may be said here, that there are nerve cells along the profundus nerve up to the point where it joins the ramus ophthalmicus superficialis trigemini and sends its fibers into the cranial cavity. Also, in Weigert preparations the profundus nerve was found to send fibers into the trochlear nerve as it passes near (fig. 25).

An interesting question arises as to the origin of the nerve cells within the cranial cavity of adult Amia. Total mounts of the nerve did not always show the cells and when found, they are quite variable in number. Moreover, it appears that the nerve fibers as well as the cells are sometimes asymmetrical as regards the two sides. In the cases noted there was greater development

on the right side of the specimen. As the cells are very much like those of the profundus nerve outside the cranial cavity, it was at first inferred that they migrate into the cranial cavity along the fibers from the profundus nerve. This seemed all the more probable because the cells inside the cranial cavity were not found in sections of young specimens, but the number of cells is very small in the adult and might be overlooked very easily in the young among so many blood vessels. There is an interesting observation to be mentioned here as having a possible bearing on the origin of the posterior group of cells within the cranial cavity. This group lies not far from the position of the evanescent thalamic nerve described by Miss Platt ('91) in Acanthias. In fact, in one Cajal preparation of adult Amia, it was thought that a few fibers of the thalamic nerve were found entering the brain laterally anterior to the habenular bodies. For some reason there was a break in the continuity of the fibers at the brain wall. Inside the brain, fibers were seen running from this point. As no evidence of a nerve in this location has been found in any other specimen the presence of a thalamic nerve in Amia is in doubt.

When the nerve cells at this point (b in fig. 25) are examined in surface views of total mounts, they are found to be well scattered. Fig. 26 shows five cells in their natural relation to one another in the most crowded portion of the ganglion of nearly twenty cells. Some of these cells are closely applied to the membranous pallial wall of the forebrain. In Cajal preparations I have found one or two nerve cells lying near the median line among the paraphysis tubes situated between the dorsal sac and the pallium of the forebrain. Fibers were often found here among the paraphysis tubes establishing what may be considered as a commissure between the two halves of the intra-cranial sympathetic system.

As already mentioned, Golgi impregnations show that the blood vessels everywhere within the cranial cavity have nerve fibers branching on their walls, but it is not so easy to determine whether the paraphysis and the ciliated epithelium of the dorsal and diencephalic sacs have their intrinsic nerves or not. The paraphysis is a glandular structure with tubes gathering to a duct which pours its secretion into the brain ventricle just beneath the middle

of the pineal stalk (fig. 30). Kingsbury ('97, a, fig. 4) shows the opening of to the duct of the larval paraphysis. There are many instances in Golgi impregnations that seem to me to show that there is an intrinsic nerve supply to its tubes (fig. 27). Fibers often lie in the closest proximity to the blood vessels on one side and to paraphysis tubes on the other. Also, fibers are occasionally found between the tubes of the paraphysis and the ciliated epithelium of the pallium (fig. 27). In the basement membrane of the dorsal and diencephalic sacs there are often found nerve fibers in the same intimate relation with the epithelium on one side and the

forebrain ventricle

ciliated epithelium

paraphysis tube

blood vessel

paraphysis tube

over 'og

FIG. 27. Golgi preparation of the meninges of adult Amia showing the relation of the nerve fibers to the paraphysis tubes and to the blood vessels near the pallial covering of the forebrain. × 200.

blood vessels on the other. The richest supply of nerves is found among the paraphysis tubes to which the majority of the medullated fibers entering the cranial cavity were traced. The next richest supply of nerves is furnished to the blood vessles near the ciliated pallial epithelium, but some fibers are found on the walls of the blood vessels in all positions in the cranial cavity.

The ciliated epithelium just mentioned merits a closer examination into its structure and function. It may be said at the outset that there is the same essential structure of the pallium of the

forebrain, of the dorsal sac, and of that side of the diencephalic sacs farthest from the brain wall. The ental side (toward the brain) of the diencephalic sacs is made up of delicate flattened epithelial cells, as Kingsbury ('97, a) has noted. Also, he has pointed out the fact that the high columnar epithelial cells of the pallium and diencephalic diverticula are glandular in appearance and that they have a more copious blood supply than the flat cells on the ental side of the diencephalic sacs.

Favorable fixations and staining in iron hæmatoxylin show that these columnar cells are ciliated (fig. 28) with from three to six long stout cilia to each cell. Portions of the live epithelium mounted in normal saline solution show that the cilia are active in producing motion in the encephalic fluid. Strips of the epithe

Katharine Hill

FIG. 28. Section of the membranous pallium of the forebrain of adult Amia. Shows the motile cilia, the granular contents of the columnar epithelium and its cuticular border. Two "mast" or wander cells are shown between the cells of the epithelium proper. Iron hæmatoxylin stain. × 444.

lium running parallel with the long axis of the brain show by the motion of the blood corpuscles which have escaped from the vessels, that the general direction is anterior in the common forebrain ventricle. Strips cut from the ventricular walls of the forebrain showed that there is ciliary action by its cells also, producing motion rostrad along the slit between the halves of the prosencephalon. Likewise, there is ciliary action on the walls of the rhinocols. The few experiments made seem to show that the return path of the encephalic fluid runs laterally from the rhinocols and posteriorly along the lateral everted portion (Kappers '07) of the forebrain. The cilia have basal bodies and the free borders of the epithelial cells possess a cuticula which is striated