50 THE AMERICAN MONTHLY [March, 



cc, and filter it before use. Place the objects in the stain, and leave them 

 for twenty-four hours ; they are then taken out one at a time, dipped in water, 

 and mounted in glycerin or Farrant's medium. 



( To be contt7iued.) 



A. new injecting mass. 



By MAURICE N. MILLER, M. D., 



DIRECTOK OF HISTOLOGICAL LABORATORY, UNIV. MEDICAL COLLFGE, NEW YORK CITY. 



I have, during the past ten years especiall}-, been using very little artificially 

 injected tissue in teaching, for the reason, first, that vascular channels so 

 filled are usually distorted by the pressure necessary to their complete injec- 

 tion ; and, secondly, the opacity of the injecting material obscures the vascular 

 walls. 



I have, rather, insisted that the student should bv persistent effort become 

 acquainted with the histology of vascular coats as they appear in undisturbed 

 relation, I would, by no means, discard injections altogether; much of our 

 present knowledge of organized structure has become possible only by the aid 

 of such preparations. But I would encourage the student to believe that the 

 most valuable sections are not those which have had their vessels plugged 

 with opaque gelatin — arteries red, veins blue ! ( .?) The students under my 

 instruction are provided with sections which they can duplicate or equal 

 when they go home and commence working by themselves. And I know it 

 is a very proud moment for the young physician when he finds himself able, 

 with the aid of a few simple and always obtainable appliances, to make, stain, 

 and mount a section — and one which will enable him to say, e. g.^ whether the 

 minute speck of growth which he has removed from a patient is a harmless 

 wart or a deadly cancer. Let us, then, beg the beginner, with all the 

 earnestness with which I am capable, to let injections alone for a year, at least ; 

 and devote such time as you are able to spare to the acquirement of the tech- 

 nique necessary to hardening, cutting, staining and mounting. 



These remarks may seem singular as prefatory to a description of an injecting 

 method. I am perfectly well aware that the student will not pay the slightest 

 attention to what I have said, but will immediately get a copy oi Beale^ and 

 borrow the farina-kettle from Bridget, make some carmine gelatin, sacrifice 

 a neighbor's pet grimalkin and fail utterly, miserably. And it's ten-to-one 

 that he never attempts injecting again — that is to say, for histological purposes. 

 Now I have devised an injecting mass which is intended to be made on the 

 day following this experience. 



First procure some thin, clear, colorless French gelatin. You will find it 

 in sheets about 3X8 inches, with crossed markings. Don't use Cooper's or 

 Cox's. They are worthless for our purpose. 



To one ounce of gelatin add ten fluid ounces of cold water. Allow the 

 gelatin to swell for an hoin-, and then place the vessel containing the whole in 

 a kettle of boiling water and allow it to remain until the gelatin melts thor- 

 oughlv. Strain through previously moistened flannel into, preferablv, a 

 flask," 



While yet warm and fluid, poiu" about half of the gelatin into another glass 

 vessel. Dissolve in one half two grains of dry common salt ; and in the 

 other half ten grains of nitrate of silver. Should the gelatin become stiffened 

 by cooling it must be warmed, and so kept ffuid. When all is dissolved 

 mix the twt) gelatin solutions and shake brisklv for from three to five minutes. 

 Add ten grains of citric acid and keep the gelatin warm until the former dis- 

 solves. This is the injecting mass and is ready for use. If the means are at 



