370 General Notes. 
THE ORIGIN OF THE Mamma.'—In this note, W. Haacke 
figures and describes the temporary marsupium of Echidna, and 
reasserts his claim to the priority of the discovery of the oviparity 
of the Monotremata. The conclusion is reached that the glands sub- 
serving a mammary function in these creatures are developed from 
sudoriparous glands, while in other mammals the mammary organs 
have been developed from sebaceous glands. Two apparently care- 
fully-drawn figures of this pouch are given, which disappears after 
the single ovum is hatched. is pouch is not to be confounded 
with that described by Gegenbaur and Owen as occurring in this 
animal, 
PHYSIOLOGY.” 
DOES THE VOLUME OF A MuscLE CHANGE During ITs CON- 
TRACTION ?—It has long been a disputed point whether or not the 
bulk of a muscle alters during its contraction. As far back as the 
middle of the seventeenth century it was the subject of investiga- 
tion by Glisson, Borelli, Swammerdam and others, but their meth- 
ods allowed of errors so great as to make their results nearly worth- 
less. The first to observe by a fairly trustworthy method that the 
volume of a muscle is slightly lessened during contraction was 
Erman, about 1812. 
Erman’s method consisted in placing the muscle in a cylinder 
filled with water, and, during contraction of the muscle, observing 
the level of the water in a narrow capillary tube connected with 
e vessel. With every stimulation of the muscle Erman noted a 
slight fall of the fluid in the capillary. Some time after this, 
Johannes Miiller suggested that the sinking of the level observed 
by Erman was caused, not by the diminution in bulk of the muscle 
itself, but by the compression of the air in the spaces between the 
fibres. Erman’s experiments were thereupon repeated by Marchand 
and Ed. Weber who eliminated this possible source of error by 
killing the animals under water. Nevertheless they still observed 
a fall of the water in the capillary, precisely as Erman had done 
before them. - 
In more recent times Kühne has reinvestigated the question, and 
employed a new method, dependent on the change in specific grav- _ 
ity which must result from any change in volume. By this method 
Kühne reached negative conclusions, for he could observe no sink- 
ing of the araometer when the muscle attached to it was thrown 
into tetanus. 
1 Bi 4 att, VIII, No. 1, ‘ : ; 
silo, nea I perea ak 
of Technology, Boston, to whom communications, books for review 
etc., should be sent. 
