periments of Dr. E. Smith show results which are hard to reconcile. He found brandy, whiskey, and gin lessened the production of carbonic acid; rum, ale, porter, tea, coffee, and cocoa increased it, a result quite opposed to the statements of Prout and Böcker. He proves that more carbonic acid is evolved in a moist air; and as this is a measure of the waste of tissue, it shows the hygienic value of a dry climate. Cod liver oil lowers respiratory waste-hence partly its efficacy in phthisis; though, if tubercle consists of unoxidised carbon, as contended for by Dr. MacCormac of Belfast, matters which increase the amount of carbonic acid would be more suitable. Inhalation of chloroform remarkably decreases the evolution of carbonic acid, and that agent owes its efficacy as an anæsthetic to its not being combustible in the blood.

4. The amount of Watery Vapour is between 16 and 20 ozs. in the 24 hours, as determined by the wellknown experiments of Lavoisier and Seguin, which also show its proportion to cutaneous transpiration. They enclosed the body in an air-tight bag, and breathed into a vessel. The amount of water thus collected was equivalent to 18 grs. per minute, of which 11 came from skin, 7 from lungs. The water is partly derived from the blood by exhalation and partly produced by the oxidation of the hydrogen in food and tissues. It holds dissolved carbonic acid-the amount of which has not been duly accounted in determining its evolution from the lungs--and a peculiar animal matter, probably albuminous, and similar in odour to the skin and blood. This fetid matter is much increased by indigestion, when some unassimilated substances are got rid of by the lungs. Odorous matters, as camphor, alcohol, turpentine, rapidly appear in the breath if swallowed, or may by inhalation be introduced into the system.

Nitrogen in air acts merely as a diluent, and according to Boussingault, is given off into expired air more frequently than absorbed.

Ammonia is also expired, as proved by breathing on a microscope glass which is exposed to the vapour of hydrochloric acid, when crystals may be obtained, and common salt and urates may be found in the pulmonary exhalation.

Asphyxia is the term by which the cessation of respiration is usually denoted, but apnoea is a more correct expression. It may result from the introduction of some gas not containing oxygen, which we have seen is essential to respiration, or from the exclusion of atmospheric air, as in drowning or suffocation. Gases are either respirable or irrespirable. The former may be noxious from excess of oxygen, from want of it, or from containing some positively injurious agent. The latter prove fatal in the same way as a mechanical obstruction, for the glottis spasmodically closes and excludes them: if in small quantity they merely excite coughing.

The chief examples of these classes of gases are here tabulated:

I. Respirable gases, injurious' by

When animals are made to respire pure oxygen their blood becomes of a bright scarlet, all the functions are excited, but stupefaction ensues from the great production of carbonic acid. Sir H. Davy discovered that nitrous oxide can be breathed for some time. It excites the nervous system, producing slight delirium and often

laughter (hence its popular name of "laughing gas"), and if longer continued stupefaction or syncope follow. Zimmerman found that animals evolved more carbonic acid when breathing this gas. Hydrogen, like nitrogen, if pure, is not in itself injurious, for if oxygen be mixed with it, animals breathe the mixture with impunity. Carbonic acid is usually supposed to produce a dark colour of the blood, and carbonic oxide a precisely opposite effect. These two gases are generated by the burning of charcoal, which is a common mode of suicide in Paris. That carbonic acid is really poisonous was shown by Rolando. He tied one bronchus in a land tortoise and the animal survived; but when he passed carbonic acid through one, and allowed the other to inspire air, death soon occurred. Arsenical gases are the most intensely poisonous, an almost inappreciable quantity having destroyed the life of Mr. Brittain, a chemist in this city some years ago.

When atmospheric air is excluded from the lungs, the movement of the blood in their capillaries almost immediately stops, and the right side of the heart and whole venous system become loaded with blood. The blood on the left side of the heart and arteries is scanty, and remains unarterialised. Prof. Draper, as before-mentioned, regards the interchange of gases in the lung as the main cause of the circulation, and thus stagnation must occur if such interchange be prevented; but circulation can again go on if air—or, still better, oxygen-be admitted. A stream of carbonic acid directed on the capillaries in the web of the frog's foot will stagnate the blood-cells within them. This effect, and their incapability of passing through the pulmonary capillaries, is probably due to the increase of size which that gas produces. Erichsen performed the following experiment, to show that some blood will still flow through the lungs from which air is excluded if the action of the heart be kept up. He pithed dogs, kept up artificial respiration in the left lung,

but tied the right bronchus; he found that as long as the heart beat, some dark blood flowed from the right pulmonary veins, and scarlet blood freely from the left. Another of his experiments went to prove that asphyxia does not depend on the passage of venous blood through the nervous centre, as he found animals died in the usual time although arterial blood was made to flow freely through them. Ackermann also has observed the condition of the brain during asphyxia, by trephining and inserting a glass plate into the aperture; he asserts that there is always remarkable anemia. It may be objected that the cranial vessels are always found full after death, but gravitation of the blood which remains fluid would account for this. Animals will live longer if merely deprived of air than if they are submerged in water; thus, drowning kills by the absence of air, the poisonous effects of the retained carbonic acid, and the entrance of water into the respiratory passages.

A committee of the Royal Medical and Chirurgical Society, which investigated this subject some months ago, found that dogs were deprived of life by being kept under water for 1 minutes. When simply deprived of air, as by plugging the trachea, respiratory movements continued for 4 min. 5 sec., and the heart continued to beat for 7 min. 11 sec., or 3 min. 6 sec. after all respiratory efforts had ceased. Rabbits afforded a complete exception to the latter fact. Dogs will recover by themselves after air has been excluded for 3 min. and 50 sec. The rapidity of death by drowning is owing mainly to the entrance of water into the lungs, and if the inspiratory efforts are enfeebled by intoxication, narcotic poisoning &c., life may be prolonged considerably. The same committee investigated the respective merits of the Marshall Hall and Silvester methods for restoring persons drowned. The former, termed "the ready method," consists in rolling the body alternately from the front to the side and back again, so as to compress the thorax

and allow it to expand again. It was found that never more than 15 cubic inches of air could be thus introduced into the lungs of a dead subject. Dr. Silvester's plan is to alternately raise and depress the arms, and thus expand and contract the capacity of the chest. As 44 cubic inches can be thus sucked in, and as the warm bath can be employed at the same time, it seems the most trustworthy.

Man's

Animal Heat.- - Organic bodies are warmed directly by the sun's rays to a degree varying with the diurnal rotation of the earth, producing day and night, and with the earth's course round the sun, producing the change of seasons. Heat is also radiated from the earth, where it is either stored up from the sun's rays or generated in the interior. But animals, and man above all, are independent of these influences, for they can produce a temperature far more equable within themselves. temperature averages about 100° Fahrenheit, or according to Brown-Sequard 103°, being somewhat higher in such internal parts as the rectum and vagina, and gradually lower as we proceed towards parts farther from the centre of the body. Dr. John Davy found it but 90° at the sole of the foot. Becquerel and Breschet showed the deeper parts had the highest temperature, by inserting wires connected with a thermo-electric apparatus; thus while the heat was 98° at 1 inches from the surface, it was but 94° at inch. They found muscle the warmest tissue, especially during contraction, when it was raised 2 or 3 degrees.

Disease alters the temperature considerably: thus, in scarlatina and fever it has attained 107°, in tetanus 110-75°, and in phthisis and pneumonia, owing to the diminished oxidation in the lungs, the skin acquires a great increase of heat. All practical physicians must have felt the "calor mordax" of acute pneumonia. Asiatic cholera and morbus cæruleus the temperature may be as low as 77° in the mouth.

In