1883.] Physiology. 1081 
with the single genus Myxine. In the Hyperoartia or Petromy- 
ontide he recognizes the genera Petromyzon, Ichthyomyzon, 
Ammoceetes, Entrophenus, Geotria, Exomegas and Caragola. 
The form of the suproval laminz is the principal character made 
use of, and Caragola, which has two such lamina, is made the 
type of a sub-family. 
PHYSIOLOGY. 
STUDY OF THE PHYSIOLOGY OF THE KIDNEY BY MEASUREMENTS 
OF ITS CHANGE OF VoLuME.—Dr. Roy has employed an ingenious 
instrument, the oncometer, devised by him on the principle of the 
plethysmograph, for the measurement of variations in the volume 
of the kidney. The apparatus consists essentially of a metallic 
box lined with a flexible membrane, in which the kidney of a 
living animal while in its normal situation can be laid and in- 
closed in an air-tight manner. The space between the kidney 
and the box is filled with warm oil which finds its exit by means 
general rise of blood pressure which accompanies Gyspnora, 
as would follow on common hydraulic principles. Division of 
e splanchnic nerves, however, does not completely do away 
With the reflex. It is very difficult to manipulate the nerves en- 
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This department is edited by Professor HENRY SEWALL, of Ann Arbor, Michigan- 
