SCIENTIFIC SUMMARY. 
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How the Actual Cautery should he used. — We fear a good many professional 
men are completely ignorant of this. We ourselves have known men who 
fancied that the iron was not to he brought even to a red-heat ; whereas 
when rightly done, it is done with a white-hot iron, pain being then com- 
pletely avoided. Dr. J. S. Camden makes the following remarks on this 
subject in the “ Medical Times and Gazette,” and, as they are worthy of 
being recorded, we give them a place. He says : — “ I see in Dr. Fayrer’s 
work on the * Thanatophidia of India ’ that the actual cautery was used 
unsuccessfully (which in another place he calls a red-hot iron). This is 
not what I was always taught and seen as actual cautery. I consulted 
‘ Cooper’s Surgical Dictionary/ edited by Lane. There it is called an iron 
in a state of incandescence, which is, according to Maunder, incipient white 
heat. jProf. Symes, in his lecture, calls it a red-hot iron. I also made many 
inquiries of medical friends, and all spoke of it as a red-hot iron. Having 
twice assisted in using, and once used, actual cautery, I hope I know some- 
thing on the subject. When actual cautery is to be used, the iron must be 
heated till it is really of a white heat, and looks almost as white as white 
paper. If then applied, it destroys the part instantaneously, giving no pain ; 
but it must be removed quickly on the heat decreasing, and then another 
iron applied. Several irons are required for use, and a fierce fire kept up 
by bellows, till your object is attained ; but if a red-hot iron only is used, 
the agony is intense, as we all know who have touched it. The first time 
I saw it used, on a girl of fourteen years, no pain was given, to my great 
astonishment ; the second time, on an elderly person (both for fungus in the 
upper maxillary bone), her screeching was fearful, till I told the operator 
his irons were not half hot enough. He then requested me to head them 
properly, which being done, not a murmur was heard. The irons were 
being used only red-hot. The last time was opening four or five sinuses in 
a favourite horse’s shoulder. He never flinched, and scarcely seemed aware 
of what was being done. The only thing he noticed — for he never moved — 
was the hissing made by the destruction of the skin. Actual cautery is 
painless. I would suggest using — to obtain the white heat for actual 
cautery — a large spirit blow- pipe.” 
Physiology of the Flight of Birds. — In one of the numbers of the u Comptes 
Rendus,” M. Marey, who is the Dr. Pettigrew of France, has a paper on the 
above subject. He used various artificial birds for experiment. Comparing 
their wing-stroke with that of corresponding real birds, he perceived that 
the former must be three or four times more rapid than the latter in order 
to raise the weight. Some condition, then, increasing the resistance of the 
air under the wing must be wanting in his apparatus. This is, he showed, 
the translation of the bird. Air shows inertia ; that is, submitted to a 
constant repulsive force, it resists strongly at first, then acquires velocity, 
which it tends to retain after the force has ceased to act. Move a light disc 
uniformly in a direction perpendicular to its plane. It may be shown with 
a registering dynamometer that there is — (1) a considerable resistance at 
the beginning, from inertia of the air column ; (2) a weaker pressure main- 
tained throughout the movement ; (3) a tendency to impulsion of the disc 
when it has stopped, from the acquired velocity of the air column. Thus 
the resistance of the air to movements of bodies consists of a regular regime , 
