274 APPARATUS FOR SECTIONING [_CH. X 



A careful stud}' of the cuts or plates used to illustrate the same class of facts 

 as one wishes to show will enable one to produce similar effects. Out- 

 lines which are transferred to the drawing paper may be obtained by the camera 

 lucida or from a photograph. The drawing should be made so that it can be 

 reduced anywhere from one-eighth to one-half. For ordinary photo-engraving 

 for such line drawings as are used to illustrate this book, use perfectly black 

 carbon ink. A shaded or wash drawing can be reproduced by the half-tone 

 process, also photographs as is illustrated by figures 190-191. A crayon drawing 

 on stipple paper with shadows re-enforced by ink lines and high lights scratched out 

 with a sharp knife give admirable results for anatomical figures by the half-tone 

 process. (See for example the work of Max Broedelin Contributions to the Science 

 of Medicine, (Welch Book) Baltimore, 1900). 



For photo-engravings of line work the letters, figures or words used to desig- 

 nate the different parts can be put on the drawing by pasting letters, etc., of the 

 proper size in the right position. In preparing the block the photo-engraver 

 eliminates all shadows and the letters look as if printed on the drawings. 



\ 437. Wax Models. — Large wax models of the objects which one studies 

 under the microscope are helpful both to the teacher and to the investigator. 

 These models are becoming more and more appreciated for embryologic and 

 morphologic investigations, for, as one can readily appreciate, the effort to produce 

 a representation of the embryo or organ in three dimensions helps to overcome 

 difficulties which are almost insurmountable if studied in the sections alone. 



They are made from wax plates, the principle involved being that the diame- 

 ter of the drawing on the wax plate is as much greater than the object as the wax 

 plate is thicker than the section. 



The wax plate is cut with a sharp instrument, following the outlines of the 

 object which has been traced upon it by the aid of a camera lucida or the projec- 

 tion microscope. The sections are piled together, some line or lines obtained 

 from a drawing or photograph of the spceimen before it was imbedded and sec- 

 tioned being used as a guide by which the correct form of the pile of sections can 

 be tested. Finally the whole is welded into one by the use of hot wax or a hot 

 instrument. Models which illustrate complex internal structures are difficult to 

 prepare, but numerous devices will occur to the worker as the representation of 

 blood vessels and nerves by strings or wires. A large model will need much sup- 

 port which can be given by wire gauze, wires, pins or paper according to the 

 special needs. 



A practical method for wax modeling was first published by G. Born, Arch. f. 

 Mikr. Anat., Bd. xxii, 1883, p. 5S4. The most detailed statements of improve- 

 ments of the method have been published by Born (B6hm u. Oppel) 1900, and by 

 Dr. F. P. Mall and his assistants. See contributions to the Science of Medicine, 

 pp. 926-1045. Proceedings of the Amer. Assoc. Anatomists, 1901, 14th session 

 (1900) p. 193. 



\ 43S. Some Apparatus for Imbedding and Sectioning. — As a supplement to 

 Chapter VIII, the following figures of imbedding and sectioning apparatus are 

 appended. It will be noticed that the microtomes are complex and consequently 

 expensive. One is figured in which the knife is moved by the hands of the oper- 

 ator (Fig. 217). This form of instrument is excellent, and with it one can do 

 all kinds of work, both with collodion and paraffin. One cannot work so rapidly 



