The amount of =Cloud= should be estimated daily, according to a scale ranging from 0 to 10, _i.e._ clear sky up to completely overcast. The form of cloud should also be stated, as cirrus, cirro-cumulus, cirro-stratus, cumulus, cumulo-stratus, stratus, and nimbus. CHAPTER XXXVI. PERSONAL HYGIENE. Certain personal factors are very important in relation to health. The chief of these are constitution, temperament, heredity, idiosyncrasy, age, sex, and habits. =Constitution.=—Health may vary in degree without the presence of actual disease. This fact is expressed by the use of such terms as “perfect,” “strong,” “feeble,” “delicate,” in speaking of the health of the same person at different times, and also as distinguishing one person from another. The constitution is an important factor in resisting disease, and a robust constitution may determine recovery from a severe illness, while the patient with a feeble constitution falls a victim to it. The constitution of an individual is partly _acquired_, partly _inherited_. A feeble or delicate constitution may be acquired by unhygienic conditions, such as deficient exercise, the prolonged breathing of impure air, unhealthy occupations, some imperfection in diet, or dissipation. But while many a robust constitution is enfeebled by such conditions, a weak constitution may happily be strengthened by careful and prolonged attention to the laws of health. This is especially well seen in the case of those who strengthen their muscular system by carefully-graduated and not excessive exercise. =Heredity= has a great influence on health. As a rule the children of healthy parents are robust, and on the contrary, any “weak point” in the parents’ constitutions is liable to be participated in by their children. Both _mental_ and _physical_ conditions may be inherited. A peculiar habit of mind, as well as the same expression of features, may be inherited. As regards physical diseases, the influence of parents is not less remarkable. The son of a gouty father requires to be particularly abstemious in order to avoid his father’s disease. Certain specific febrile diseases, _e.g._, enteric fever, diphtheria, and still more rheumatic fever, are hereditary in the sense that the members of certain families are more prone to them than others. Insanity, epilepsy, asthma, neuralgia, and hysteria are also hereditary in the same sense, and it is noticed that they occasionally alternate in different generations. Cancer, consumption, certain skin diseases, and a tendency to the early onset of degenerative diseases, appear also to occur more often in certain families than in others. In most cases it is the tendency to disease which is transmitted, and not the disease itself. When an actual disease is inherited, as happens very rarely in tuberculosis and often in syphilis, the actual infection is transmitted before birth from the parent.