We are still in the dark as to what causes the spasms but undoubtedly psychic factors {210} play an important etiological rôle. For a good many people, there is a distinct element of dread as the immediate cause of their asthmatic attacks. Some people have it only when they have gone through some disturbing neurotic experience. Occasionally it is the result of physical factors combined with some psychic element. Cat asthma is not very uncommon and occurs as a consequence of some contact by the individual with a specimen of the cat tribe though usually the large cats, the lions and tigers, do not cause it. There is nearly always, in those who are liable to this form of asthma, a special detestation of cats. There is probably some emanation from the animal which produces the asthmatic fever, just as is true also of horses in those cases where horse asthma occurs. In a few of these latter cases, however, it was noted that the horse asthma did not begin until after there had been some terrifying experience in connection with the horse, as a runaway, a collision, or something of that kind. Any one who sees many asthmatic cases inevitably gets the impression after a time that their very dread of the attacks has not a little to do with predisposing them. {211} Occasionally the dread is associated with some other organic disturbance, either of heart or kidneys, or oftener still, with some solicitude with regard to these organs and the persuasion that there is something serious the matter with them, though there is at most only some functional disturbance. This is particularly true of cases of palpitation of the heart where there has been considerable dread of organic heart disease. In a certain number of these cases, there is some emphysema present, that is, overdistention of the lungs, such as is seen in high-chested people. Owing to the long anterio-posterior diameter of the chest and the fact that as a consequence it is nearly as thick through as it is wide, this form of chest is sometimes spoken of as barrel-chest. Patients who have it are particularly likely to suffer from asthma if they have any dread of heart trouble or if they are of a nervous constitution.