Hayden — On Respiration of Compressed Air. 201 
of the conditions requisite for the experiment, and the difficulty of 
artificially constructing a suitable apparatus for the purpose. 
Tabarie in 1838 demonstrated by a series of experiments that great 
and progressive condensation of the air surrounding the body, and 
breathed by it, has the effect of slowing the pulse and the respiration, 
and of lowering the temperature of the body, both subjective and 
objective. 
In 1850 Pravaz showed that under a pressure increased by half au 
atmosphere, the pulse sensibly falls, sometimes by two-fifths, respira- 
tion becomes slower but more ample, muscular contraction acquires 
more energy, and there is increased exhalation of carbonic acid up to 
a pressure of ten to twelve centimetres, above which limit it is di- 
minished. He found, moreover, that on leaving the condensed air- 
bath, the exhalation of carbonic acid was again increased, and attained 
its maximum on^y a certain time subsequently. 
Longet declares that many of these results are not intelligible, 
and need confirmation." 
In the building of the bridge of Kehl a few years ago, Bucquoy 
made observations on himself and others, as to the effects of breathing 
compressed air. He noted restlessness and a feeling of oppression, ir- 
regularity of breathing, consisting in abbreviation of the inspiratory, 
and prolongation of the expiratory act, quickening of the pulse and 
palpitation, pain in the ears as if from the impaction of a foreign 
body, and so severe as to make the subject cry, impairment of hearing, 
and voice of a nasal quality and requiring an effort ; the movements of 
the limbs were easier than natural, and under a pressure of two and a 
half atmospheres it was impossible to whistle, and there was copious 
perspiration. 
The pain in the ears alternately went and returned till it finally 
ceased, and simultaneously the breathing became tranquil. 
On returning into the open air he experienced a feeling of cold, 
the breath formed a dense cloud, there was a return of palpitation 
and irregularity of breathing, and likewise of pain in the ears, all of 
which lasted only a few minutes. 
The air consisted of Oxygen, . . . . . . . . 19-23, 
Mtrogen, 80-77, 
and contained a large excess of carbonic acid, amounting to more than 
two parts in a hundred. 
The labourers lost flesh and appetite, and experienced muscular 
pains, and symptoms of congestion of the brain and lungs. Blood 
drawn from the veins was in some instances bright red, especially after 
long exposure to compressed air. 
By means of the sphygmograph and the ophthalmoscope Dr. Burdon- 
Sanderson has ascertained that the effect of inhaling compressed air is 
to diminish the volume of blood in the veins and auricles, and to in- 
crease that in the arteries and ventricles. Hence, he infers, it is 
useful in the. treatment of pulmonary emphysema, chronic bronchitis, 
R. I. A. PROC. — VOL. II., SER. II., SCIENCE. 2 D 
