TWO DISPUTED POINTS IN THE HISTOLOGY OF THE SUBMAXILLARY GLAND. MEMBRANA PROPRIA—NERVE-ENDINGS (WITH PLATE.)[[1]]
BY CHR. SIHLER, M. D., PH. D., CLEVELAND, OHIO.
Formerly Fellow of the Johns Hopkins University.
The submaxillary gland is of importance not only for its own sake, but because its anatomical connections and situation are such that it can be subjected to physiological experiment, and a number of important results have been reached which I may discuss at some future time.
[1]. Read before the Cuyahoga County Medical Society, January 7, 1886.
The results of my work are not only contradictory to the authorities in histology, but also do not harmonize with the requirements of prevailing physiological theories. Bringing this before you does not mean that I ask you to accept either facts or conclusions. I am fully aware of the difficulty of such work, the doubtfulness of the facts and the liability to error in the conclusion. But it is just possible that some of the younger members may fare as I did—have not all their time occupied by practice—and if I enlist the interest of any in this most important region I shall feel happy.
A number of years have passed since I undertook this question, and the work on the nerve-endings on muscle, which I had the pleasure to communicate to this society a few months ago, was undertaken more as a study, to make myself familiar with analogous structures, than that I expected to find anything new.
METHOD.
In the investigations on the nerve-endings I used the submaxillary of the half-grown cat, the calf, the ox and the puppy. The method followed was in the main that of Beale. In the case of the cat I injected the whole animal from the aorta with Turnbull’s blue, dissected out the gland, duct, and the nerves entering it. After breaking up the gland into pieces by aid of a needle, from the size of a bean to a pea, I placed it in a dish with a light cover, containing Beale’s carmine (carmine dissolved in ammonia and glycerine). I am in the habit of using a stronger solution than Beale’s. I suspect that the carmine I used in some of these stainings was adulterated with eosin, and that possibly this may have been of advantage. In some of my stainings I used a fluid prepared from cochineal; used ammonia in dissolving the coloring matter, and then added carmine besides. It is of the utmost importance to have no excess of ammonia present, otherwise the staining will be slow and imperfect. I have been staining with this method for years, yet I cannot say why the results differ so much. Some time ago I stained a frog for the nerve-endings in muscle and obtained the most beautiful results, but in the number of stainings I have made since (trying to follow the same method) I have not been by far as successful as then. In breaking up the gland I do not always separate all the pieces, but try to remove the connective tissue holding together the small lobules with the dull end of a needle, and then throw the coherent mass into the stain. In this way I procured a very perfectly injected and beautifully stained submaxillary of a half-grown cat, from which I made a number of valuable specimens. The material may remain in the staining fluid for weeks, and may be examined every two or three days to note how the staining is advancing. When the masses stained are large, or the whole gland is subjected to staining, of course the outer parts are more deeply stained than the inner ones, but it is at times convenient to have material of different depths of staining. After the process has continued long enough—the nuclei at least should be very distinctly colored—the material is transferred into a fluid containing glycerine five parts, water and alcohol each two parts, acetic acid one part. Here it may remain about twenty-four hours, and finally it is to be preserved in a similar mixture containing but a trace of acetic acid. I hold acetic acid of varying strength diluted with glycerine in high esteem in such investigation. It does two things, removes the superfluous stain and softens and clears up the connective tissue. Thus treated, the material is ready for examination.
The tissues thus prepared may be hardened in alcohol and sections cut, but this will not aid much in the investigation of the questions that interest us. For this purpose teasing and compression with the cover glass are mainly to be relied upon. It is to be commended to isolate one of the little lobules the gland is composed of, because thus we certainly have ready for examination all the elements making up the gland. The little root which connects the lobule with the rest of the gland will consist of the duct, vessel and nerves supplying the lobule. Such a lobule is broken up with needles and by compression between slides. All these manipulations are to be carried on in glycerine. When the fragments are small enough they are examined with lower powers. The ducts in well injected specimens can be recognized by the rich supply of vessels, the nerve-trunks by the arrangement of the nuclei.