Columbia University School of Dental and Oral Surgery - Dental Columbian Yearbook (New York, NY)

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YEAR BOOK of writing a few pages and labelling them a history just be- cause others have stupidly done so. There is no such a thing as a history. For that means recording something that is gone and past-dead. Nothing is ever dead. In fact the incidents that occurred during the past three years of college will hence- forth be more alive than they were even while they were actually occurring. They will now live in the imagination and each one will have a personal interesting manner of seeing them. All of which is infinitely more interesting than getting them down in one black and white form. Moreover how could one possibly write the history-the past-of one hundred and thirty human beings who are first to go out and accomplish their deeds '? Perish the thought! Let others who will, write histories,-not I. This has only been the whim of a momentg an interesting and pleasant pastime: a winding thought that turned every now and then aside to get some pleasure out of a particular impression and then continued. . . . M. A. JAGENDORF. HERE AND THERE. A freshie once was asked to give By Youngs rule. I was told, The dose of some mild laxative For a child eleven months old. So this is what the freshie did And thought it quite a stunt: - He found the dose for a year old kid And marked it, Wait a month. M. M. A STRANGE BUT TRUE HISTORY OF OUR CLASS OOM sy OUR POOR EDITOR

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A STRANGE BUT OF OUR CLASS TRUE HISTORY NINETEEN SIXTEEN sion: the stigma of misbehavior. I can hardly frown at the accusation. True, at times the behavior was more fit for the kindergarten than a professional school, but then it must never be forgotten that it was but the expression of exuberant youth,-and nothing appeals to 'this historian' more than youthfulness. To act youthful is the only way to beat old age and perhaps -arterio-scelerosis. So, if at times We did act rather like very young children than men and women of science, let it be remembered that even lustful noise is pref- erable to morose, serious faces. Then I might have turned to the real gist of the history. I might have taken up individual records. Each and every member of the class might have received a careful, just, and admirably written short history. It would have commenced with as early a time as possible and gone thru all mental and physical development and material progress up to the moment when this goes down on paper. If possible I should have in- cluded all the important events of those who had any iniiuence on their career: fathers, brothers, sisters, mothers, sweet- hearts. Nor should I have omitted talking of the surrounding influences and the hereditary influences. In other words, the record would have been as complete as it possibly could be. I should have commenced something like this: Profes- sionally the student of the nineteen sixteen class may be read- ily divided into three large classes. Those who study with a serious purpose,-be it because of the interest in science, or the interest in a serious purpose in lifeg or because the work particularly appealed to them. Then there are those who study because they are to derive an immediate benefit-say pecun- iary. . .social. . . And so, good readers, I have given you a fair example of the kind of history I might have written. Are you not thank- ful for having confined myself to the few short lines which you read in the first paragraph fthe secondj I wrote. Of course there may have been a few with a literary turn of mind who could have preferred my many pages of printed lines-to those I apologize and will add a word of comfort and joy: Some day they may yet have the opportunity. When I have no more to worry about examinations and practical 'required cases' I shall turn to write a complete and unabridged history of the class of nineteen sixteen. My models will be Gibbons and Clara Steichen. But one more word before I close. Of course this was no history. I cannot do what is impossible nor would I be guilty A 18

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NINETEEN SIXTEEN COLLOIDAL COLLOIDAL CHEMISTRY-SOME DENTAL APPLICATIONS. CHEMISTRY C :OLLOIDAL chemistry concerns itself with a SOME DENTAL study of the fine subdivisions of matter APPLICATIONS I!-o after a certain stage. A colloidal solution I'l 5 is one in which the particles are so finely subdivided that they remain in permanent 65-gg:-g9.g,,' suspension. This definition permits of the assumption that any substance can be suffi- ciently subdivided to represent a transformation into a colloid,i' which assumption has been verified. Sodium Chloride, a typical crystalline substance, can be transformed into a colloid by such a subdivision. Thus we see that there is no sharp demarcation between colloidal and ordinary chemistry but rather a transition. With the advent of the ultra-microscope great strides have been made in the study of this comparatively new branch of chemistry. Under the ordinary high power micro- scope, the smallest particle visible has a diameter of one tenth of a micron, which is taken as the distinguishing limit between precipitates and colloids. With the ultra-microscope, par- ticles become visible whose diameter is four tenths of a milli- micron. This means four ten millionths of a millimeter, an inconceivable dimension. The principle of the ultra-micro- scope is very ingenious and easy to comprehend. If a beam of light is thrown across a totally darkened room, one may ob- serve the dust particles of the air in rapid vibratory motion. This phenomenon can be accentuated by throwing a handful of mica particles within the beam. Instantly bright irride- scent particles are seen dancing in the light, producing a fas- cinating spectacle. This principle is the distinctive feature of the ultra-microscope. The ray of light is allowed to pass parallel to the stage across a dark field instead of being re- flected directly thru the lens by the mirror. The latter method has the disadvantage of dazzling the eye and thus obscures the vision. A common example of this is our failure to see the stars during the day on account of the superior brilliancy of the sun. The physical difference, therefore, be- tween the ultra-microscope and the ordinary microscope is that the former makes use of the principle of refracted light while the latter is based on the principle of reHected light. The most interesting feature of the ultra-microscopic particles is their tremendous rate of movement which increases directly with their decrease in size. The most common form of movement is the Brownian, characteristic of the cocci germs, which, indeed, represent colloidal particles. 20