bing and wringing of the clothes are then required; but the clothes must be well rinsed after the washing and aired out-of-doors, or a slight odour of kerosene (when kerosene soap is used) is retained in the fabrics. The paraffin soaps are free from this defect. The grease and dirt cannot be removed from clothes (no more than they can be removed from the skin owing to the fatty secretion from the sebaceous glands at the roots of the hair follicles) by merely washing in water without the use of soap. The alkali of the soap (soft soap is an oleate of potash; hard soap is a stearate of soda) combines with the grease and emulsifies it, whereby it is easily washed off, whilst the fatty acid. prevents the too great removal of the oil from the wool fibres and the deterioration of the fabric. Cheap soaps, containing an excess of alkali, are bad for the skin, for it is rendered over-dry and loses suppleness by excessive removal of sebaceous secretion, and they are also injurious to woollen fabrics by carrying away the animal oil contained in the fibres.

In Merino, wool and cotton are mixed in varying proportions. "Shoddy" is old used and worked-up wool and cloth.

Silk (fig. 66) is a bad conductor of heat, but is less absorbent than wool. It presents some advantages for under-clothing, as it is more cleanly and shrinks less than wool, and is less irritating to the skin; but it cannot hold perspiration like wool. It is besides expensive, and is less durable than cotton or merino.

Leather and Waterproof Material.—These are invaluable for exposure to very cold bleak winds and rain. Leather is most suitable for very cold climates. Being impermeable they are extremely warm, but this im-. permeability prevents the ventilation and renewal of

the layers of air confined under the clothing near the skin. The discomfort that arises from the wearing of waterproofs in warm weather is well known.

In hot climates the outer garments should be white or grey in colour to protect from the direct rays of the

sun.

At the two extremes of life-in childhood and old age -warmth of covering is most essential. Children lose heat rapidly and are liable to chill, partly because the

FIG. 66.-Silk Fibres X about 200.

circulation being rapid more blood is carried in a given time to the superficial vessels, and more heat is thus lost from the surface, than in an adult; but mainly because in children the surface of the body is larger in proportion to its bulk or contents, than is the case in adults. Consequently, a larger surface proportionally being exposed, from which heat can be radiated, children

must be more warmly clothed than grown-up people. A simple example will serve to illustrate the above fact. If two cubes are taken with sides of one square foot and two square feet respectively, it is evident that the smaller cube exposes a surface of 6 square feet, and has a bulk of I cubic foot; or surface is to bulk as 6 to I. The larger cube exposes a surface of 12 square feet, and has a bulk of a little less than 3 cubic feet; or surface is to bulk as 12 to 3, or 4 to I.

The same is true when applied to cylinders which more nearly resemble the human body. If two solid cylinders are taken, both 10 inches in length, but the smaller having a base I inch in diameter, and the larger

FIG. 67.-Hemp Fibres X about 200.

a base 2 inches in diameter; in the smaller cylinder, surface is to bulk as 33 to 8; in the larger, surface is to bulk as 66 to 32. That is to say, the larger cylinder has 4 times the bulk of the smaller, but only twice the surface.

Children should be clothed in woollen materials, and the legs, arms, neck, and chest should be equally protected with the other parts of the body.

In old age the circulation is often feeble and languid, and the functions of heat production and regulation are less efficiently performed than before senile decay commenced. Consequently if the body is chilled, the restor

ation to the normal heat is slow, and the vital functions are dangerously depressed.

Aniline dyes are now largely used for colouring various dress materials and under-garments such as stockings. As a rule the dyes used are free from arsenic; but it has occasionally happened that eczematous sores have been produced on the feet and legs by wearing dyed stockings, and there can be but little. doubt that the sores were due to the absorption of arsenic through the skin when the feet were hot and damp.

CHAPTER IX.

THE CONTAGIA: COMMUNICABLE

DISEASES AND

THEIR PREVENTION: HOSPITALS.

THE CONTAGIA.

CERTAIN diseases of men and animals have long been known to be communicable from one individual to another, and recent investigations have shown that some of these diseases are not only communicable from one individual of the same species to another, but are interchangeable between animals and men, and between men and animals. Various doctrines have been held at different times as to the nature of the contagia in these diseases, but the theory of their constitution which is embraced in what is known as the "germ theory of disease" need only be discussed here, as being the most recent enunciation of the scientific study of disease causation, and as possessing certain easily intelligible inherent possibilities which are from the earlier beliefs on this subject. Whilst endeavouring to supply an explanation of such facts as are known about infection or contagion by the aid of the germ theory, it need not necessarily be assumed that any such doctrine is capable of satisfactorily explaining every occurrence in disease dissemination, or that a finite settlement of a very profound and complex subject has been arrived at. It is more than probable that the future will bring forth modifications and alterations in principle and detail, which will deprive the views, at