THE RELATION OF THE CORTEX OF THE CAT’S KID- 
NEY TO THE VOLUME OF THE KIDNEY, AND AN 
ESTIMATION OF THE NUMBER OF GLOMERULI. 
W. S. MILLER, M. D., and E. P. CARLTON, B. S., 
Instructor in Vertebrate Anatomy, Graduate Student in Histology . 
University of Wisconsin. 
In the following study the kidneys of twelve cats were used; 
four pair were used fresh, four pair were hardened in Muller’s 
fluid and four pair, after being injected with blue gelatin, were 
hardened in alcohol. All the animals were chloroformed and 
bled. The kidneys that were hardened in Muller’s fluid and in 
alcohol were used to determine the per cent, of cortex as shown 
by area, while the per cent, as shown by volume was estimated 
on the fresh kidneys. The per cent, of cortex as shown by area 
was also estimated in the fresh kidneys. 
FRESH KIDNEYS. 
The kidneys were removed from the body, all fat carefully cut 
away, the vessels cut close to the hilum and the volume o 
each kidney found by displacement. The length of each kidney 
and the distance from hilum to convexity of opposite surface was 
found by placing each kidney on a piece of sheet cork and erect¬ 
ing perpendicular needles at the several points and measuring 
the distance between the needles. One of each pair of kidneys 
was taken and cut into five or six pieces transversely and the 
exact thickness of each section found by the use of needles; the 
sum of the thickness of the several sections equaled the total length 
of the kidney as previously determined. 
The separate sections were then taken one by one and covered 
with a large glass slide; they adhered to this without difficulty 
and without distortion. The slide was then fastened in a special 
table in such a manner that the surface of the glass opposite 
the section of kidney was on a level with the surface of the 
table. The outline of the section and the boundary line between 
