320 Generat Notes. [ March, 
Dr. Lauder Brunton describes a simple experiment, but not one 
very easy to verify, by means of which rhythmical contraction 
and dilatation of the capillaries in man may be demonstrated. If 
the finger-nail be drawn once or twice up and down the mid- 
dle of the forehead a red streak remains which may persist 
many minutes. This streak undergoes variations in width and 
brightness, some of which correspond to the heart-beat, others to 
the movements of respiration, and still another series have a 
slower rhythm of some twenty seconds interval; these last 
changes probably have their origin in purely local contractions of 
the capillary walls—//. Physiology, Vol. v, p. 14. 
THE Piston RECORDER. — Schafer describes a very simple 
device for registering graphically the variations in volume of a 
frog’s heart, which may find quite general application. The organ 
whose changes of volume are to be measured is inclosed ina 
vessel filled with fluid which communicates with a horizontal 
glass tube of 3-4 ™ diameter containing oil. A disk of platinum 
fits closely in the tube and is in contact with the oil column whose 
movements it follows perfectly without allowing the escape of oil 
round its rim, An aluminium rod of proper length, bearing a 
writing point at one end, is fastened to the center of the platinum 
disk, and the piston rod passing through a hole in a cap at the 
end of the glass tube is kept moving in the center of the latter. 
—Jt. Physiology, Vol. v, p. 130. 
THE ORIGIN OF FIBRIN FORMED IN THE COAGULATION OF BLOOD. 
—Research upon the cause of blood clotting has been rendered 
very difficult because of rapidity of the process of coagulation in 
the blood of most animals. Dr. Howell has discovered that the 
blood of the terrapin clots very slowly and offers unequaled advan- 
tages for the study of its chemical changes. A sample of this blood 
- single chemical body, fibrinogen, which exists pre-formed in the 
blood plasma, into fibrin under the influence of fibrin-ferment, 
which is a product of the dissolution ot white blood corpuscles. 
—Stud, Biol. Lab. Fohns Hopkins Univ., Vol. iti, p. 63. 
VOLUNTARY ACCELERATION OF THE HEART-BEaT 1n Man.— _ 
which the rate of heart-beat seems to have been under easy con- 
2 _ trol of the will. As is well known, the pulse rate and character 
is normally profoundly influenced by the emotions, and there is 
~ little doubt that in most of the cases recorded the alteration in heart 
rhy thm was brought about indirectly through the excitement 
of the appropriate psychical condition. In fact, simple concen- 
3 h ttenti n on the heart r 
is sufficient. in mos 
i 
