Ch. XI] SERIAL MICROSCOPIC SECTIONS 403 



series are made so that the object can be seen in three dimensions, 

 the models also serving to make it easy to follow out the relations 

 of parts with the naked eye. But one should not forget that a model, 

 like a drawing, is after all only the interpretation of the artist and the 

 thing itself must be referred to whenever there is to be real ad- 

 vancement in knowledge. Furthermore, as it is not possible to both 

 dissect and serial section the same object, and sometimes very few 

 are available, anatomists have decided on the three planes which 

 give the greatest information, — transections or cross sections, 

 sagittal sections, and frontal sections. With sections in these three 

 spatial planes it is possible to gain some just conception of the 

 actual relation of parts and structures in the object. 



§ 657. Orientation of imbedded objects. — In order that sections 

 may be made in any desired plane the object must be so arranged 

 or oriented in the imbedding mass that one can attach the imbedding 

 block to the microtome holder, and then arrange for sectioning in a 

 definite manner. With translucent or transparent collodion where 

 the position of the object can be seen after it is imbedded, this is not 

 particularly difficult, but with paraffin, which is nearly opaque, one 

 cannot see distinctly enough the position of the object to give the 

 exact arrangement necessary to make precise sectioning possible. 

 The embryo or animal or other object must therefore be arranged 

 in the imbedding box in a very definite manner. 



To overcome the difficulties Dr. Kingsbury, ten to fifteen years 

 ago, devised the method of making a diagram of the object to show 

 its exact shape and position. (Anat. Record, Vol. XI, 1916, p. 294). 

 The method is as follows: A natural-size diagram of the object is 

 made on the inside of the bottom of the imbedding box before any 

 paraffin is put into it. This is most easily done before the box is 

 folded, or the folded box can be unfolded and made flat again. For 

 making the diagram a soft lead pencil can be used or one of the or- 

 dinary colored crayons or a colored glass pencil. In any case enough 

 of the lead pencil or the crayon mark adheres to the paraffin to make 

 a clear diagram on it of the object. 



In imbedding, the object should be arranged exactly over the dia- 

 gram. The solidified layer of paraffin formed before the object is 



