I am aware that these tumours in the lungs have been ascribed to scrophula. But the frequent occurrence of consumptions in persons in whom no scrophulous taint existed, is sufficient to refute this opinion. I have frequently directed my inquiries after this disease in consumptive patients, and have met with very few cases which were produced by it. It is probable that it may frequently be a predisposing cause of consumption in Great Britain, but I am sure it is not in the United States. Baron Humboldt informed me, that the scrophula is unknown in Mexico, and yet consumptions, he said, are very common in that part of North-America. That tubercles are the effects, and not the cause of pulmonary consumption, is further evident from similar tumours being suddenly formed on the intestines by the dysentery, and on the omentum by a yellow fever. Cases of the former are to be met with in the dissections of Sir John Pringle, and one of the latter is mentioned by Dr. Mackittrick, in his inaugural dissertation upon the yellow fever, published in Edinburgh in the year 1766[23]. [23] Pages 7, 8. 4. The catarrh is of two kinds, acute and chronic, both of which are connected with general debility, but this debility is most obvious in the chronic catarrh: hence we find it increased by every thing which acts upon the whole system, such as cold and damp weather, fatigue, and, above all, by old age, and relieved or cured by exercise, and every thing else which invigorates the whole system. This species of catarrh often continues for twenty or thirty years without inducing pulmonary consumption, in persons who pursue active occupations. 5. In the hereditary consumption there is either a hereditary debility of the whole system, or a hereditary mal-conformation of the breast. In the latter case, the consumption is the effect of weakness communicated to the whole system, by the long continuance of difficult respiration, or of such injuries being done to the lungs as are incompatible with health and life. It is remarkable, that the consumptive diathesis is more frequently derived from paternal, than maternal ancestors.