No. 2.] CHANGES IN THE SPLEEN OF THE FROG. 40 1 



Methods of Determining the Curves.^ 



a. Size Cin"-oes. 



As was stated above, care was taken to make sections 

 through the largest diameter of the spleen. The largest sec- 

 tion of every spleen was selected and drawn with the camera 

 lucida upon millimeter paper. The instrument used was a 

 Zeiss stand with eyepiece 4 and Leitz objective i. The tube 

 of the microscope was always of the same length and stood 

 perpendicular to the drawing surface. The angle of the mirror 

 was carefully regulated. The section was placed as near 

 the center of the field as possible, before it was drawn. 

 The number of square millimeters included within the 

 outline of the section was then counted, the result thus 

 obtained becoming the elements of the preliminary or individual 

 curves. 



b. Blood Curves. 



The quantity of blood in the spleen was taxed according to 

 the relative proportion of the red-blood corpuscles and the 

 size of the blood-vessels and capillaries to the remaining tissue 

 of the spleen. If the spleen was judged to contain about equal 

 parts of blood tissue and spleen tissue, this was indicated by 

 10 on our scale ; if the proportion was }{ spleen tissue to 

 ^ blood tissue, we noted 15; if Y\ spleen tissue to J^ blood 

 tissue, 5. 



c. EosinopJiiloiis Cells. 



The frequency of their occurrence was determined as fol- 

 lows : A large thin section was selected, and since the " eosin- 

 ophilous " cells are especially abundant near the surface of 

 the spleen, I counted the number occurring in as broad a zone 

 near the circumference of the section as I could well oversee 



1 The simplest method of determining the size of the spleen, that of weighing 

 it, could not be practically adopted, because of its minuteness and the fear of 

 disturbing the microscopical structure. The form of the spleen is, further, so 

 irregular that it would scarcely have been more accurate to estimate the volume 

 from the area or diameter. 



