16 Woodworth: Graphic reconstruction from serial sections. XIV, 1. 



the measurements can be multiplied to any extent, reconstructions 

 to any seale can be produced with any eombination of objective 

 and ocular. The method is somewhat restricted in its application, 

 for it can be employed best only with symmetrieal objects, and more 

 especially with transverse sections of objects having bilateral syni- 

 metry. However, the method is simple, rapid, and accurate, and if, 

 as will appear later, a portion of theobject can be sacrificed in 

 order to secure a plane of definition, it is also applicable to imsym- 

 metrical objects. 



For the purpose of Illustration, we will assume that we liave a 

 series of transverse sections through a small trematode, from which 

 it is desired to show by reconstruction on a frontal plane the course 

 of the intestinal tract at a magnification of 100 diameters. We will 

 assume that the worin is 2 mm in length and that the intestine is 

 of the simple bifurcate type, as in the genus Distoma ; also that the 

 sections are 20 (i in thickness, and that we are to measnre them 

 by means of a Zeiss objective AA, ocular micrometer 3, and a 

 tnbe-length of 160 mm, the valne of one division of the ocular 

 micrometer nnder these conditions being 17*2 {.i. On a sheet of 

 paper draw a line 200 mm in length , which shall represent the 

 chief axis of the worin one hundred times enlarged, and at right 

 angles to this draw 100 parallel lines at intervals of 2 mm 

 (= 20 /< X 100), representing the planes occupied by the sections. 1 

 By means of the ocular-micrometer the greatest diameter of each 

 section is now measured, multiplied by 100, and half the resulting 

 distance marked off on each side of the line representing the chief 

 axis and along that one of the parallel lines which corresponds to 

 the section on which the measurement was made. For example, 

 the diameter of section 23 is 0*588 mm, 2 which multiplied by 100 

 equals 58'8 mm", half of which is 29*4 mm. This distance, then, 

 is marked off on the twenty third of the parallel lines and on both 



1 ) The proceedure so far is the same as that introduced by His 

 (Anatomie menschlicher Embryonen Bd. I, 1880, p. 10). — It is simplest to 

 employ metrically mied, profile or cross-section paper, such as is used 

 by engineers. 



2 ) Found by multiplying the value of one division of the ocular-micro- 

 meter (17-2 (x) by the number of divisions covered by the diameter of the 

 object. In Computing thcse measurements it will be found convenient to 

 have prepared a table of the values of the ocular-micrometer divisions for 

 each of the nine digits. 



