PRESIDENTIAL ADDRESS. 633 
By a series of observations made on rats confined in cages fitted with small, 
ill-ventilated sleeping-chambers, we have found that the temperature and 
humidity of the air—not the percentage of carbon dioxide or oxygen—deter- 
mines whether the animals stay inside the sleeping-room or come outside. When 
the air is cold, they like to stay inside, even when the carbon dioxide rises to 
4 to 5 per cent. of an atmosphere. When the sleeping-chamber is made too hot 
and moist they come outside. 
The sanitarian says it is necessary to keep the CO, below 0°01 per cent., so 
that the organic poisons may not collect to a harmful extent. The evil smell of 
crowded rooms is accepted as unequivocal evidence of the existence of such. 
He pays much attention to this and little or none to the heat and moisture of 
the air. The smell arises from the secretions of the skin, soiled clothes, &c. 
The smell is only sensed by and excites disgust in one who comes to it from the 
outside air. He who is inside and helps to make the ‘fugg’ is both wholly 
unaware of, and unaffected by it. Fligge points out, with justice, that while 
we naturally avoid any smell that excites disgust and puts us off our appetite, yet 
the offensive quality of the smell does not prove its poisonous nature. For the 
smell of the trade or food of one man may be horrible and loathsome to another 
not used to such. 
The sight of a slaughterer and the smell of dead meat may be loathly to the 
sensitive poet, but the slaughterer is none the less healthy. The clang and jar 
ot an engineer’s workshop may be unendurable to a highly strung artist or 
author, but the artificers miss the stoppage of the noisy clatter. The stench of 
glue-works, fried-fish shops, soap and hone-manure works, middens, sewers, 
become as nothing to those engaged in such, and the lives of the workers are in 
no wise shortened by the stench they endure. The nose ceases to respond to the 
uniformity of the impulse, and the stench clearly does not betoken in any of 
these cases the existence of a chemical organic poison. On descending into a 
sewer, after the first ten minutes the nose ceases to smell the stench; the air 
therein is usually found to be far freer from bacteria than the air in a school- 
room or tenement. 
If we turn to foodstuffs we recognise that the smell of alcohol and of Stilton or 
Camembert cheese is horrible to a child, while the smell of putrid fish—the meal of 
the Siberian native—excites no less disgust in an epicure, who welcomes the cheese. 
’ Among the hardiest and healthiest of men are the North Sea fishermen, who 
sleep in the cabins of trawlers reeking with fish and oil, and for the sake of 
warmth shut themselves up until the lamp may go out from want of oxygen. 
The stench of such surroundings may effectually put the sensitive, untrained 
brain worker off his appetite, but the robust health of the fisherman proves that 
this effect is nervous in origin, and not due to a chemical organic poison in the air. 
Ventilation cannot get rid of the source of a smell, while it may easily dis- 
tribute the evil smell through a house. As Pettenkofer says, if there is a dung- 
oD in a room, it must be removed. It is no good trying to blow away the 
smell. 
Flaigge and his school bring convincing evidence to show that a stuffy 
atmosphere is stuffy owing to heat stagnation, and that the smell has nothing 
to do with the origin of the discomfort felt by those who endure it. The 
inhabitants of reeking hovels in the country do not suffer from chronic ill- 
health, unless want of nourishment, open-air exercise, or sleep come into play. 
Town workers who take no exercise in the fresh air are pale, anemic, listless. 
Sheltered by houses they are far less exposed to winds, and live day and night 
in a warm, confined atmosphere. 
The widespread belief in the presence of organic poisons in the expired air is 
mainly based on the statements of Brown Sequard and D’Arsonval, statements 
wholly unsubstantiated by the most trustworthy workers in Europe and America. 
These statements have done very great mischief to the cause of hygiene, for they 
led ventilating engineers and the public to seek after chemical purity, and 
neglect the attainment of adequate coolness and movement of the air. It was 
stated that the condensation water obtained from expired air is poisonous when 
injected into animals, The evidence on which this statement is based is not only 
not worthy of credence but is absurd, e.g., condensation water has been 
injected into a mouse in a quantity equivalent to injecting five kilogrammes into 
