"4. A stooping or otherwise constrained posture while at work, exemplified in lace-makers, throwers of earthenware, certain classes of weavers, file-cutters, and silk-piercers.

"5. Working continuously many hours daily at a sedentary occupation, such as that of the glove-makers of Yeovil, decorators of earthenware, and welters and finishers of hosiery.

"6. Working in ill-ventilated and over-crowded rooms, as in the straw-plat and lace schools of Berkhamstead, Towcester, and Newport Pagnell, the winding rooms of Leek, and the weaving shops of Hinckley and Leicester.

"7. Residing in dwellings so constructed that the bedrooms are badly ventilated, and the cubical space per head is inadequate to the preservation of health, such as are to be found in Berkhamstead and Saffron Walden.

"C. 1. Bleakness of climate, a cold damp soil, prevalence of fogs.

"2. Marriages of consanguinity.

"3. Habitual abuse of alcoholic stimulants.
"4. Insufficiency of animal food."

Although certain parts of this summary have no immediate connection with the subject-matter in hand, it has been given in extenso, to show how frequently several causes of disease co-operate in producing the same pathological results, and how difficult it is to apportion to these causes their relative share in the combined effects. But, apart altogether from the unwholesome influences attaching to particular employments, the one great fact which stands forth with special

prominence throughout the whole of Dr. Greenhow's inquiry (see also Fourth Report to Privy Council), is the fatally defective state of the ventilation, alike of cottage, workroom, and of busy factory. The mortality from lung-disease amongst male and female operatives was found to be from three to six times as great as in other districts of England; and in a very large proportion of cases the want of ventilation in dwelling-places, as well as work-places, prevailed to such an extent, that tubercular and scrofulous diseases must have resulted abundantly from this cause alone.

The medical officer of the Privy Council, in commenting on this inquiry, remarks-" One must remember that, in most cases, either the artisan's ill-ventilated work-place is also his ill-ventilated dwelling-place, or else the dwelling-place to which he goes for his rest is as ill ventilated as the work-place which he leaves; that during a great part of the year the work-place has artificial light in it, in many cases gaslight for some hours of the day, and in some cases has its atmosphere vitiated by other products of combustion; that in factories during winter the commonly adopted method of warming is one which in itself makes the air unpleasant, if not hurtful for breathing; and that in many branches of industry good ventilation is essential as a safeguard against evils which are special to the employment-essential for the removal of injurious dust, or for the abatement of an oppressive temperature."

In all these industrial employments it thus appears that the sick-rate and death-rate could both be very materially lessened by promoting ventilation, and by introducing some suitable appliances calculated to protect the workmen from the inhalation of fine dust or

noxious fumes. But it was found that the workmen themselves often objected to any innovation which appeared to them to interfere with their more immediate comfort; and not a few of them were under the impression that the introduction of any measures tending to prolong life would be followed by such an overstocking of the labour market, that the difficulties of procuring a living would be greatly increased. That such shortsightedness will continue to exist amongst certain numbers of the artisan class is only what may be expected. Disease sets in so insidiously and progresses so slowly, the stock of health to start with seems so ample, and the individual prospect of death so remote, that sanitary rights are neglected and the wrongs quietly endured. Hence the remedy for such wide-spread evils must be supplied from without,-by rigorous sanitary inspection under the provisions of sanitary laws. (See concluding Chapter and Appendix.)

CHAPTER IV.

VENTILATION AND WARMING.

THESE two subjects may be conveniently treated under the following sections:

I. The Amount of Fresh Air required.

II. The Necessary Amount of Cubic Space.
III. Natural Ventilation.

IV. Artificial Ventilation and Warming.

SECTION I. THE AMOUNT OF FRESH AIR REQUIRED.

As the air contained in an inhabited room cannot, under the most favourable circumstances, be maintained in as pure a condition as the external air, the object of ventilation is to reduce the impurities of respiration to such an extent that continued inhalation of them will not be detrimental to health. While this can only be effected by a constant supply of fresh air, it is evident that the quantity required will very much depend on the amount of impurities which may be allowed to accumulate in respired air without proving injurious. The first point, therefore, which has to be determined, is the limit of maximum impurity consistent with the maintenance of perfect health. It has already been shown that the amount of carbonic acid in air vitiated by respiration is a tolerably reliable index to the other impurities; and hence the question resolves itself into this, What amount of carbonic acid shall be accepted

as the standard of permissible maximum impurity? After numerous experiments, and a most extended inquiry, Dr. Parkes has given it as his opinion that, allowing 4 volume as the average amount of carbonic acid in 1000 volumes of air, this standard ought not to exceed 6 per 1000 volumes; because, when this ratio is exceeded, the organic impurities, as a rule, become perceptible to the senses. With a ratio of 8, 9, or 1 per 1000 volumes, the air smells stuffy and close, and beyond this it becomes foul and offensive. Dr. Parkes observes, "I admit that I am not able to show by direct evidence, that impurity indicated by 7, or 8, or even 1 volume of carbonic acid per 1000, and organic impurities in proportion, is injurious to health. We possess no means of testing the effects of such small quantities. Such a standard must be adopted, first, on the general evidence that large aerial impurities are decidedly hurtful, and that smaller amounts may be presumed to be so in proportion, although we cannot measure the action; and, secondly, on the fact that we have an obvious and simple measure in the effect produced on the senses, which gives us a practical line of demarcation we could not otherwise obtain." (Practical Hygiene.)

Perhaps there is no class of buildings which present better opportunities for arriving at an approximate and practical solution of this problem than prisons; and it may prove of some service if I record briefly the results of some experiments which I have had a share in conducting, and which are strongly corroborative of Dr. Parkes' views. In one of the convict prisons one-half the prisoners are kept in separate confinement, except when at exercise, the other half are confined in their cells only during the night and when at meals.

The