400 Chronicles of Science. [ July, 
of speech, and that though when this is injured, by long trial the 
right side may be made to do its work, yet m the normal state the 
right side takes no very active part. He compares the case to the 
attempt to use the left hand for writing, when the right hand, which 
has been trained to work with facility, has been injured. M. Broea’s 
argument is certainly ingenious, and will doubtless give phrenolo- 
gists some hope of yet mapping out the convolutions of the brain 
to their respective “ faculties.” 
The Sohygmograph, which is exciting some attention just now, 
is one of those ingenious instruments which have been devised of 
late years, promising really to assist medical men in reducing their 
art to something like a science. Its great merit is this, that it 
gives a permanent and minutely accurate record of a phenomenon 
which before was known only by the very unsatisfactory discrimi- 
nation of the sense of touch.* . 
The sphygmograph is an instrument for producing a self- 
written record of the swellings and contractions of the arteries 
known as the pulse. Its inventor, Dr. K. J. Marey, is a Paris phy- 
sician, who is well known for many valuable physiological essays. 
The main features presented by the instrument are the followmg :— 
A principal beam of light construction is fastened on the arm by care- 
fully padded straps ; to this is attached a lever of nearly the length 
of the fore-arm; the shorter arm of this lever rests gently but 
firmly on the pulse; at each rise of the artery and subsequent fall 
the motion is exactly imparted to the lever, and the end of the 
longer arm performs the same movements as does the shorter, but 
ona much larger scale. To the end of the longer arm is attached 
a fine-pointed pencil, in contact with which a smooth strip of paper 
is made to move by clockwork in a horizontal direction. The effect 
of this arrangement is, that a straight line would be drawn on the piece 
-of paper were it not for the rhythmic perpendicular movement 
caused by the pulse, which results in the production of an undulated 
line, the waves in which represent the separate expansions of the 
artery ; of course, it is evident that smce the movement of the paper 
is invariably uniform, the variations in the pulse will be distinctly 
indicated by the height, length, and form of the waves ; and accord- 
ingly we have a most accurate and valuable means of comparing the 
pulse in various individuals and under various circumstances. Some 
interesting results have been obtained by studying the pulses of 
diseased persons, and the mstrument has been found to exhibit phe- 
nomena in the pulse which it was quite impossible to detect by the 
rough-and-ready means of the fingers. . The “ sphygmogram” of a 
person afilicted with a certain disease of the heart, for example, is 
found to exhibit a series of undulations, the ascending line of which is 
*¢On the Use of the Sphygmograph in the Investigation of Disease.’ By 
Balthazar W. Foster, M.D., M.R.C.P. Lond., Professor of Ciiniecal Medicine in 
Queen’s College, Birmingham. 30 pp. Crown 8vo. 
