The name itself has been used in part only, apparently to describe some form of A. spinulosum Sw. (spinulosum-americanum Fisch., MS., Index Fil. Moore, p. 104) but whether applied to the present form or to our American plants in general as the name implies, I have no means of knowing. Moore gives as a synonyme var. B. of Lastrea dilatata, a fern generally regarded as a distinct species by English authors.

But whatever may have been its application in that form, in bringing it forward here under the present combination, it becomes an entirely new and as much an original name as if it had never been used at all.

I have been led to restore A. Boottii to its specific value, and to retain Tuckerman's name for it from the following considerations:

The characters that seem to connect it with cristatum are, when more carefully examined, really no stronger than similar resemblances between other and good species.

For example, the sterile fronds of A. munitum of the Pacific States, and our northern A. acrostichoides are quite as much alike as the sterile fronds of Bootti and cristatum. Our common A. marginale and the Californian A. argutum sometimes so closely resemble each other as to suggest a closer relation than is accorded to them. These two species and A. filix-mas often appear to run together, having many similar resemblances, yet they are all three undoubtedly good species. Similar and equally strong resemblances may be found existing between many other species, and the puzzling forms of the small Botrychia are sufficient to show how little dependence can be placed, at times, on external appearances alone.

It is sometimes difficult to distinguish small specimens of Cheilanthes lanuginosa from Notholana Parryi, and not an uncommon thing for fronds of Woodsia obtusa and Cystopteris fragilis to become mixed through their close resemblance, and if this occurs among species belonging to entirely different genera, how much more likely is it to occur among closely related species. So that I cannot see why any argument drawn from such resemblances should have more weight in this instance than in those mentioned.

Few ferns are really more distinct than A: Boottii. Its individual character is even more pronounced than that of A. inter

medium, and there is seldom any difficulty in distinguishing it at all times from all other ferns by which it may be surrounded. Its wide-spread distribution in this country and Europe (where it was first discovered and described as a species by Braun, under the name of Aspidium remotum, and where it seems to preserve its character no less distinctly than with us) entitles it to a higher consideration than that of a mere variety, and although its resemblances to cristatum are stronger than its resemblances to spinulosum, the glandular indusia keep it always distinct from the former species. In no instance known to me is there any record of glandular indusia occurring in cristatum while in Boottii they are always present.

Its anomalous character, however, occupying as it does an apparently intermediate position between spinulosum and cristatum, and the fact that it is generally found growing in company with those two species, has led many to regard it as a probable hybrid, but a proper consideration of this theory will show that while it may be possible for those two species to hybridize as frequently as this theory would pre-suppose, it is hardly probable that they should do so in so many instances, and under such widely different circumstances and surroundings without producing some other than this one particular form, everywhere so uniform in its character. But even this theory, if established, would only result in raising our plant to the dignity of a species, a position to which I think it no less entitled now.

I retain Tuckerman's name, as it is the only one by which our plant is generally known to American botanists, and having been used frequently abroad, it has the additional merit of being the best known and most widely used of all names.

Finally, if it be urged against my paper that, as my investigations have apparently been limited to Middlesex County, they can only be regarded as partial, I answer that those observations were made upon living plants growing in their natural situations, and other examinations of a series of herbarium specimens from Maine, Vermont, Massachusetts, New York and other States, have only strengthened my convictions in regard to them.

During a recent visit to Portland, Me., I visited a number of rich swamps in the neighboring towns and found A. americanum to be the prevailing form in that vicinity. I met with A. spinulosum but twice, and in both instances the specimens were well marked and characteristic.

Some of the specimens of A. americanum were remarkably large and fine, and might have been mistaken for dilatatumwith. which form large specimens are no doubt often confounded -but a close examination revealed all of the characters that I have described as belonging to this species.

:0:

PLASTER OF PARIS AS AN INJECTING MASS.1

THE

BY SIMON H. GAGE, B.S.

HE necessity for some artificial, colored medium to fill the blood vessels must have been felt by the first anatomists. Indeed, injections were rudely made by Eustachius and Varolius in the sixteenth century (Turner, I, I, 812).2

It was left, however, to De Graaf and Swammerdam to fairly initiate the process in the middle of the seventeenth century (Turner, I, I, 812).

De Graaf used mercury and colored fluids, and was the inventor of the injecting syringe (2, XVII, 291); but it is to Swammerdam that anatomists owe most, for he introduced the use of colored wax (2, XL, 477 and I, I, 812). This answers fairly the requirements of an injecting mass, as it may be used in the fluid state, but becomes solid very soon afterward. Upon renouncing anatomy for mysticism, Swammerdam gave his secret to Ruysch, his fellow countryman (2, XL, 477), who perfected the art, and fairly approached in skill and excellence of results the refinements of modern anatomy (1, I, 812, and 2, XXXVII, 143).

About the middle of the eighteenth century, Monro primus published an essay on anatomical injections (4), in which were given very precise directions for the manipulation and preparation of the injecting mass. It was composed of wax, tallow, oil and turpentine, colored with vermilion, verdigris or lamp-black (3).

In the latest works which treat of the technology of injections (5, 6 and 7), nearly the same formulæ for injecting masses are given; and except a mere mention of gypsum in Martin (7, II, 99), all coarse masses are solid at ordinary temperatures and must

1 This paper is based upon investigations made in course of the preparation of a Manual for the Dissection of Cats, by Prof. Burt G. Wilder and the writer.

2 See list of works referred to at the end of this paper. The first figure designates the number on the list; the last, the page; the middle, Roman numeral, the volume.

be heated before use. The subject must also be thoroughly warmed.1

Plaster of Paris has long been used as an injecting mass, in the medical schools of this country at least. It seems to be admirably adapted to this purpose from its well known property of becoming solid when mixed with water.

Although plaster has not the defects of the masses that require warming before use, there are difficulties in its manipulation. I have been unable to find anything upon the matter in books; and gentlemen connected with medical schools say they do not know of any printed directions; but this process of injecting, like other expedients is handed down by tradition from one demonstrator to another. All that I have been able to learn from others of the technology of plaster injections is that the plaster should be mixed to a thin paste with water (with a saturated aqueous solution of arseniate of soda at one medical school) and used, uncolored or colored with vermilion or red lead, very quickly before it has time to set.

The lack of precise information as to its manipulation, and the skill and certainty necessary to use simple plaster and water, from its rapid setting, render it hardly manageable by students. Yet it is so simple and excellent for coarse injections that some careful experiments were made, in the anatomical laboratory of the Cornell University during the last college year, to render it practicable, if possible, for the use of students by elucidating the following particulars:

1. The character of the plaster to be used.

2. The proportions of plaster and fluid.

3. The best and cheapest red and blue colors.

4. The means by which the plaster may be kept fluid ten to thirty minutes after mixing without preventing it from hardening finally.

5. The precautions necessary in making permanent the preparations injected with the plaster mass.

(1.) It was found that the very finest plaster is best, and indeed necessary if it is desired to fill the smaller vessels.

(2.) Equal volumes of plaster and fluid give the best results. This forms a very fluid mass which penetrates finely and sets firmly.

1 According to Martin and Frey (7, II, 101 and 10,174), fine cold flowing injecting masses may be made by dissolving copal and mastic resin, with a small proportion of wax, in sulphuric ether, and coloring with red lead; or by dissolving the finest red sealing-wax in absolute alcohol. These masses harden as soon as the ether or alcohol soaks into the tissues.

A thicker mass is much more difficult to manage. A slightly greater proportion of fluid may be used if the finest vessels are to be filled. The fluid includes all the liquid used in mixing the mass; viz, coloring liquids, restrainers and water.

(3.) As to the red and blue colors, there are several that answer admirably. For red, vermilion or red lead ground in a mortar with a little water to get rid of lumps may be added in sufficient quantity to give a bright color. A saturated aqueous solution of magenta or red aniline is the easiest to use of all the red colors. It does not diffuse and color the tissues as one might expect, but colors the walls of the vessels a very bright red. An ammoniacal solution of carmine is, however, the best red. A sufficient quantity of this is added to the mass, and then the carmine is precipitated with fifty per cent. acetic acid. The acid should be poured into the colored mass, with constant stirring, till the color changes to the bright red of dry carmine, and there is a distinct odor of the acid. It is necessary to precipitate the carmine, as an alkaline solution diffuses through the walls of the vessels and stains the surrounding tissue. The advantage in precipitating the carmine in the mass is its uniform diffusion. The same method is employed in coloring red the finest gelatin masses for histological injections (9, 10 and 11).

A saturated solution of Berlin blue is the best blue, but as this is difficult to prepare (8, 403, 9, 164 and 10, 180), the ordinary Berlin or Prussian blue of the shops will answer if it is ground with water to a homogeneous paste. The simplest blue is, however, a saturated aqueous solution of blue aniline.

The aniline colors are the easiest to use, as it is simply necessary to add to the mass a sufficient quantity of the solution to produce the desired tint.1

(4.). It has been known a long time that if alum or borax is burned with gypsum, the resulting plaster will not set for three or four hours after mixing, but will finally set nearly as hard as marble (12). It is said by Tomlinson (13, I, 829) that ordinary plaster may be kept fluid four or five hours after mixing with water by adding a little size or beer; and it is a matter of common experience that the greater the proportion of water the longer it takes the plaster to set. It is necessary to give the mass a cer

'Leamon's red and blue aniline dyes answer very well, and may be bought at any drug store.