what is known regarding sensory structures in the epithelium of mammals. At once the well-known results of Connheim (Virchow's Archiv xxxviii, 1867) and Hoyer (M. A. 1866, also A. f. M. A. ix 1873) with regard to the nerves of the cornea occur to us, which prove that the nerves really enter the epithelium. Besides this, Langerhans (Virchow's Arch. xliv, 1868), demonstrated in man the entrance of nerves into the epithelium covering the body. He describes the nerves as entering the rete mucosum and then passing upward between the epithelial cells. He describes also peculiar stellate bodies which he thinks are very probably continuous with the nerves, on account of their chemical reaction. Podocopaew (A. f. M. A. v. 1869) confirms the results of Langerhans for the rabbit in all essential points. Eberth (A. f. M. A. 1870) likewise supports the investigations of Langerhans in the important particulars, and believes that no terminal network exists, but that the nerves end free in the epithelium. Chrschtschonowic (Sitzbericht. d. Wiener Acad., Feb., 1871) says that the nerves enter the vaginal epithelium and there form plexuses. Elin (A. f. M. A. vii, 1871) says that the nerves enter the epithelium of the mucous membrane of the mouth and join cells "in the upper part of the rete mucosum" fibres, also passing to the upper part of the epithelium. Eimer (A. f. M. A. viii, 1872) described the nerves as entering the epithelium of the teat of the cow, and believes them to be continuous with the "Langerhansian bodies." Perhaps more interesting than all, however, are the results of Eimer (Ibid. vii, 1871) with regard to the snout of the mole. This investigator describes the nerves as entering the epithelium covering the snout and passing upwards. The epithelial cells immediately above the entrance of the nerves are arranged in a circular manner, so as to present somewhat the form of a cylinder, thus producing a specialized structure. Eimer tells us that whenever a nerve-fibre passes one of these cells, it presents a bulbous enlargement or swelling, and finally terminates by such a swelling in one of the cells.

Now, whether the nerves end free, end in plexuses, in the Langerhansian bodies or the cells of Eimer, of one thing we are certain, and that is that the ultimate sensory structure is in the epithelium, a conclusion which, it is needless to say might have been predicted on "a priori" ground.

I think it well now to present the interesting results of Meckel

(A. f. M. A. xii), as at least a possible, if not a probable method, of explaining the touch-bodies; i. e., the corpuscles of Krause, of Meisner and Wagner and the Pacinian bodies. Koelliker tells us that they are all probably modifications of one and the same thing, as intermediate forms exist all over the body. Now Meckel describes cells as existing in birds and mammals into which he directly traces nerve-fibres. He designates them as "touch-cells" and describes their transition into touch bodies. The touch-cells are situated ordinarily beneath the epithelium, but in the bill of the pigeon they present every transitional stage between cells entirely buried in the sub-epithelial tissue, cells partially extending into the epithelium, and cells entirely enclosed by the epithelium. Again, in the snout of the hog the "touch-cells" are all in the epithelium, though in its lowest layers. They are larger than nervecells generally, and frequently two or more become joined so as to form twin cells or a more complex arrangement. These last are found beneath the epithelium. Then he also describes structures made up of a larger number of cells, but in which the nerve-fibre still supplies each individual cell. Then he describes others which are still more complex and in which the separation into cellular elements is still less apparent. All the complex forms are beneath the epithelium, only the single cell is found in the latter.

If the results of Meckel are correct, we have a link between the sensory structures of the epithelium and the touch-bodies, and the latter might be looked upon as epithelial structures in reality, but which have become displaced in the progress of development. The legitimacy of such an inference, however, would be rendered highly doubtful by the existence of the Pacinian corpuscle in the mesentery of the cat. To these last structures Arndt (Virch. A. lxv, 1875) ascribes a very peculiar significance, but which is hardly satisfactory. From observations on foetal cats he comes to the conclusion that the Pacinian corpuscle is an outgrowth of the vascular system of the mesentery.

Let us now turn our attention to a field that has been thus far neglected; namely, the organ of sight. The retina, though not developed from the epithelial layer of the embryo, is yet produced by an outward growth of another portion of the same layer. To this, however, I think we should not attach too much importance.

In all the retina of vertebrates two elements among others appear to be constant, namely, the layer of rods and cones and one corresponding to the layer of external granules. Each rod and each cone is thus connected with a cell element, and certainly it requires no great stretch of the imagination to see here a structure corresponding to a hair-cell. We have a cell with a central and peripheral process which last bears an apparatus to receive the immediate impression of force. Besides evidence by no means ends here. In those invertebrates whose eyes approach and even exceed in their complexity those of vertebrates, as the gastropods and cephalopods, the same elements remain constant, namely, the rods with their cells (Schultze, A. f. M. A. v, 1869), (Babuchin, Würzburg Verh'dlg, 1865) (Hensen Z. f. W. Z. xv, 1865).

We must remember also that in the eyes of molluscs the relation of the rods to the eye is exactly the reverse of that in vertebrates; namely, they point directly forwards and constitute the innermost layer of the retina, while in vertebrates they point directly backwards and constitute the outermost layer. This fact assumes great significance when we learn what is known concerning the development of the eyes of molluscs. Hensen says (Z. f. W. Z. xv., 1865), that the eyes of cephalopods probably originate in the same manner as the ear and nose of vertebrates, i. e., by an inflexion of the epithelial layer. In the nautilus, he says, it is evidently the case, while for the gastropods this has actually been observed in a pulmonate snail of the Phillipines, by C. Semper1 (quoted by Hensen).

When we are told by Boll (A. f. M. A. v, 1869, supplement), that the epithelium of molluscs everywhere contains haircells continuous with nerves, it would seem to place the morphological value of the rods and cells in these animals beyond a doubt. Boll describes what he calls the "neuro-epithelium." He pictures stiff, non-vibratile hairs, distinct from vibrating ciliæ, and surmounting elongated nucleated cells. They occur all over the surface of gastropods and cephalopods, being more thickly situated in parts used for apprehension or contact, as the arms of the cuttlefish and the edges of the foot of the snail. Flemming (Ibid. v, 1869 and vi, 1870) corroborates Boll's statements in the main points, though he differs from him in the detailed description of the hairs.

1 Semper has written a separate paper on molluscan eyes, which I could not obtain.

Boll also, although he determined the direct nervous continuity of the hair-cells in the ears of these animals, did not establish the nervous connection of the hair-cells in the epithelium. Flemming described long central outrunners, which can be drawn out from the sub-epithelial tissue to a comparatively great length, and which become more or less varicose in preparations treated with potassium bichromate and osmic acid. He also describes the sensory cells of pulmonate snails, but in these the hairs do not reach above the surface of the epithelium, apparently a modification to suit external conditions.

Judging from the above, we have, to say the least, good grounds for including the percipient structure of the organ of sight in the same generalization as that of the other sensory organs. As regards the other layers of the retina, may they not be simply of ganglionic value? The comparative simplicity of the retina of molluscs seems, in cephalopods, to be counterbalanced by the existence of a ganglion just before the optic nerve enters the eye. Again, the ganglionic character of the olfactory lobes may be of equal value. Indeed, this comparison might assume importance when we remember that both the olfactory lobe and the retina are processes of the cranial vesicles.

Conclusion.-In casting a last glance at the sensory organs they seem to arrange themselves more or less readily into groups. Thus, the side organs or mucous canals, the Savian vesicles and the organ of hearing, seem to constitute a sub-division by themselves. The organs of taste and smell seem to constitute another, while the eye seems to occupy a third sub-division alone. With regard to other sensory structures it would be hazardous to make any suggestions.

On the ground of certain principles that I have expressed, and of others even far more general, we may be led to suspect from the very beginning the common genesis of sensory organs; and it was a sincere conviction in the truth of such principles that led me to read the literature bearing immediately upon the subject, and to learn in how far such an opinion is supported by fact. How much it is supported by the results of the investigators which I have adduced, and the possible relations I have pointed out, I will leave you to judge.

[NOTE. The literature referred to in this paper is that only which pertains directly to the questions in point. One or two papers I

have been unable to obtain and have quoted them from others. I have knowingly omitted none that seemed important or the results of which seemed to contradict the general views suggested by the writer, with perhaps the single exception of the paper of C. B. Reichert (A. f. A. and Ph., 1871), who thinks that the early differentiation, in the embryo, of the epithelial layer and the central nervous system destroys all probability of the nerve endings being in the epithelium. How much his opinion is supported by fact, the more recent literature as adduced will enable you to judge. He rejects, in consequence, altogether the nerve-termination in the organ of hearing, as held by most observers, and even denies that the nerves pass through the openings in the zona perforata! a fact which every investigator with whom I am familiar admits and which I have myself witnessed. Reichert is the only one to my knowledge who so radically denies the results of the other investigators. To me the general agreement among so many observers, in such varied fields of research, seems to point unmistakably to some one underlying truth.]

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PLANTS USED BY THE INDIANS OF THE UNITED STATES.

BY DR. EDWARD PALMER.1

The first paper upon this subject by the writer was published in the Report of the Department of Agriculture for 1870. The present paper will embrace all the additional matter that has since come under his observation.

Fruits and Nuts.-Juniperus pachyphlaa Torr., one of the finest ornamental Junipers, its wood being excellent for cabinet work; height about forty feet, and diameter from two to three feet. Abundant in Arizona. Its fruit, a staple article of food among the Indians, is sweet, having but little of the juniper taste. As soon as ripe the Indians commence to eat the nuts raw, and to lay up great quantities for winter use. They are then ground fine and made into bread.

7. Californica, a dwarf but showy evergreen. Southern Californian Indians consume immense quantities of the fruit

1 The writer wishes to acknowledge his obligations to Prof. Asa Gray; Mr. Sereno Watson, of Cambridge, Mass.; Dr. C. C. Parry, Davenport, Iowa, and Dr. George Vasey, Department of Agriculture, for kindly determining the species.