We have still little knowledge of the causes of chlorosis, though innumerable theories as to its origin have been propounded at different times. Its onset has been ascribed to gastric indigestion, to constipation and auto-intoxication, to defective development of the sexual or of the vascular organs, and to functional nervous disturbances of various kinds.

The disease occurs mainly, if not exclusively, in girls, and as a rule in the years immediately following the onset of menstruation, though relapses are not uncommon during the succeeding decade. It affects all ranks of society from the highest to the lowest, and an hereditary tendency may be noticed, the women of successive generations being sometimes affected, and often more than one member of an individual family. Chlorotics are not necessarily unfertile, indeed they are often the reverse; and an attack, if fully recovered from, seems to have no influence on the duration of life.

It is manifest that a disease of this description can hardly be related to defective development of the sexual or vascular viscera, and digestive disturbances, however important they may be, and no one doubts their influence, can evidently have no essential bearing, or they would produce similar symptoms in the opposite sex. The cardinal factor in the etiology must be a sexual one, and any theory which assumes the contrary necessarily falls at once. But, although many theories have been brought forward, the evidence available is still insufficient to supply a satisfactory answer.

Although the essential factor is still unknown, a large mass of information is now available with regard to the secondary, or contributory, causes. In probably the majority of cases the personal hygiene is found to have been defective.

Chlorosis is thus peculiarly common among domestic servants, perhaps as a result of their long hours of indoor work, of physical exertion out of proportion to their physique, of insufficient amount of sleep, or imperfect ventilation of their living or sleeping rooms. But it is by no means infrequent among girls reared in comfortable homes, where these causes should apparently be inactive. The comparison may however be apt; lawn tennis and riding may represent the physical strain; balls and entertainments may allow little time for sleep; and the hot air of the theatre or crowded drawing-room may be even more vitiated than that of the kitchen. Overwork may be mental as well as physical, and long school hours and constantly recurring examinations may exert their own pernicious influence.

At this particular stage of development dietetic errors are apt to occur, for the girl is passing from the strict supervision of the schoolroom to the freer habits of the adult, and " the likes and dislikes" of the child are apt, in consequence, to be perpetuated, and even accentuated. Schoolroom routine, too, may prove disadvantageous, for although, as Pawlow has shown, suitable digestive secretions are elaborated for each individual meal, still gross variations in the diet cannot at once be accommodated, and digestion in such cases is necessarily imperfect; and the consequent discomforts may provoke still further deviations.

The diet of chlorotic girls thus almost invariably requires close supervision. In the majority of cases it will be found to be defective, and as a rule the protein and fatty intake is deficient, while the carbo-hydrate consumption may be excessive; the total quantity, too, is sometimes insufficient. In a small number of cases the diet is actively injurious, such substances as vinegar, dry rice or coffee, or highly spiced and seasoned foods, forming the large proportion of the daily diet.

Dietetic errors may, of course, arise from other causes than the mere whim of a growing girl, and among hospital patients, poverty and ignorance are probably the most important.

In another large group of cases gastro-intestinal symptoms occur, and exaggerate any initial error. In many cases they seem to precede the onset of the disease, and they have been considered by some as its cause rather than as its result; but they not infrequently ensue subsequent to the onset, and in other cases again may be wholly absent throughout the whole illness.

Gastric symptoms are the most frequent, and may be of varied severity. In the slighter degrees a feeling of fulness after food, flatulence and eructations, are the main features, but actual pain, more or less severe, and vomiting, sometimes persistent and repeated, may be experienced; and in a small proportion, definite evidence of gastric catarrh or ulceration may obtain.

Intestinal symptoms are also common. Constipation occurs in greater or less degree in probably more than half of all cases; diarrhoea is comparatively rare; while flatulence and colic are not uncommon, and are usually associated with stools that are offensive in their odour, and abnormal in their colour and consistence.

Various explanations of these symptoms have been brought forward, and careful examination usually reveals some abnormality in the gastro-intestinal tract. The teeth, for example, are often wanting, and thorough mastication may be impossible; or they may be carious and septic, with surrounding inflammation, or even pyorrhea alveolaris. It is always advisable to examine the mouth thoroughly after the removal of any artificial teeth. The cheap dentists, whom servants girls attend, often saw off carious teeth flush with the gums, and 'apply a plate on the top; and a row of ivory white incisors may conceal a hidden septic focus, which, however, generally gives evidence of its presence by the offensive odour of the breath.

Careful examination of the stomach may reveal abnormal conditions. It is sometimes enlarged, or displaced downwards or to the side; and the gastric secretions are very frequently imperfect. There is still some discussion as to the usual findings, but the hydrochloric acid is often excessive, rarely of average amount, and occasionally deficient or even wholly absent.