In some cases we can trace the impoverished condition of the blood to unhealthy dwellings, impure air, want of exercise, improper diet, nervousness, the reading of exciting, amorous novels, and the practice of masturbation or self-abuse. On the contrary, the disease is often developed under the most moral and exacting discipline and hygienic surroundings. I have known girls who lived in the country, enjoyed horseback riding, ate nutritious and wholesome food, and whose solitary moments were beyond suspicion, yet at the age of puberty they commenced to fade in color, and fail in strength, gradually growing paler and weaker, until they became chlorotic and bloodless. This can only be explained on the theory that the period in which nature was preparing the system for the purposes she had in view, caused a shock to the nervous system, which so disarranged the functions that the _sanguineous_ system did not respond to the growth of the _generative_ system. Then there is another class of cases, where girls menstruate before they are old enough, and without their bodies showing any visible evidence of developed womanhood, who belong to the most obstinate cases for successful treatment. The relative diminution of the red blood cells to the healthy standard is in some cases truly alarming. In the average healthy blood, there are, in one thousand parts of blood, one hundred and thirty parts of red blood cells; this falls to sixty, and even forty parts in the thousand in the chlorotic patient. It is one of the peculiarities of this disease, that while the muscular tissue wastes away, the fatty tissue is not only preserved, but it sometime increases, so that in a family of several girls, the chlorotic girl is considered the ‘_most fleshy_,’ but as fat is not flesh, the appearance is deceptive. When we stop to think a moment, that the _red blood corpuscles_ are the messengers which absorb the oxygen in the lungs during the respiratory movements, and carry it to the different organs and tissues of the body, without which all tissue change would cease. And that the same red blood cells must return again to the lungs for exhaling the carbonic acid, one of the waste products of tissue growth, then the diminution of the red blood cells in the proportion above given, must affect the entire system very injuriously. This is indeed the case; the natural respiratory movements are insufficient on the slightest exertion, so that patients tell us that when they walk a little fast, go up the stairs, or even sweep the room, they feel a shortness of breath.